From patchwork Tue Apr 8 18:49:41 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 879490 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A9AA023E355; Tue, 8 Apr 2025 18:50:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744138233; cv=none; b=UkOIu3HBX0cYvjeZhMh0g4dFtptQsihQfuG1J3iicNeFM/lF1J2ip2aDTTromijmgyhPcfwo3iOyamF7Jysj2OGOjPPQfjglGVRetHaXBsnSc/v/J7+NiEGLJSin4QizcaCrpEJpdQiq+1i2dwPNeN4Vmg0IVdPFG7zjHtBfM3o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744138233; c=relaxed/simple; bh=WNu0OLOihMi+UEPYq0gT9FeK408SxvwJ3tMV5PWv/8o=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=gNZU+iREjJW0HQkw1aM23pThjVs2DkZmHgEM8hM8mg4TZRqZm2l4NVyRYwpMy0LikUJEP8ZiruJSgEZ7fkRm+/bBDP/ar9XpbvZvH82xVYEwGqNzMeCM0YZw4QvfJeJf5CVmOE/U/orOP/fe8spHjRuJ5YtXmDYCVechlztrCIs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XoBj7oXp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XoBj7oXp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C7615C4CEE9; Tue, 8 Apr 2025 18:50:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744138233; bh=WNu0OLOihMi+UEPYq0gT9FeK408SxvwJ3tMV5PWv/8o=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=XoBj7oXp3aAUQPybwQMvhowIrWkQsu3M/VXLLMKKetElgaGPRkQQgpSTjduEp/RAS 12NoanFP4eqy1aXPC53kYNncp5VnDS/wu4yS/1SJ+ZMWsUoCKytF5FHu9G1q+ya3NU Y/pDhLUccgG7z6WEVjOg/LqSrQFWjFNmyPwbFd1WMibhfTm36eyNJTO6O81wNA9O4b twn8Z6QFiDNEVvA14U/3ajo+f1ouSL3g5ggp3ZE+NhvZoXu0ggqyXU+THs8ERVe0y1 u7XU3ne37f8APwkH3NAEeSbLskkGtB4PJFFU2xyvuJbN016FTU6fvVNOGvzf1QyoqL LkASWjzoJNtEA== From: Mark Brown Date: Tue, 08 Apr 2025 19:49:41 +0100 Subject: [PATCH RFT v15 1/8] arm64/gcs: Return a success value from gcs_alloc_thread_stack() Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250408-clone3-shadow-stack-v15-1-3fa245c6e3be@kernel.org> References: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> In-Reply-To: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook X-Mailer: b4 0.15-dev-c25d1 X-Developer-Signature: v=1; a=openpgp-sha256; l=3763; i=broonie@kernel.org; h=from:subject:message-id; bh=WNu0OLOihMi+UEPYq0gT9FeK408SxvwJ3tMV5PWv/8o=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn9W/n6ufqyLgsgInF8ZD+5fIkfiiGYCVBwgAb4b8X Nnl15KCJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ/Vv5wAKCRAk1otyXVSH0PSCB/ 97i8ET2zbFqaxwWDPoK8/6zu97L6hph6N4F6QBFPJfJeW8lQYXYNT2UhykRsnOkPtr9jItCtMqmeLv zHRfHFAC9TjRoMt0ENqQhLCKsZxo/53I59faIm5dA5668xHJigy+ZRw1ZqcKkBrr2JXQdp9vqet7o0 pBFfelz3NKmc7450ivtofptjiAaSgI526fYfuPpBGKzkS5gdIXq3WlkMYUh4LkBLyyPchMEpflJllZ NtifICfnr5RepMSrGRB0IlRAJOKFvsu0WJVxas4dU0PgLb/ZrjmxctsMAnsH+v1bUmQ14lJiFnXZ2I ih0gdXncClZqK4Hv4qqLZdrBimq+Br X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Currently as a result of templating from x86 code gcs_alloc_thread_stack() returns a pointer as an unsigned int however on arm64 we don't actually use this pointer value as anything other than a pass/fail flag. Simplify the interface to just return an int with 0 on success and a negative error code on failure. Acked-by: Deepak Gupta Reviewed-by: Catalin Marinas Signed-off-by: Mark Brown --- arch/arm64/include/asm/gcs.h | 8 ++++---- arch/arm64/kernel/process.c | 8 ++++---- arch/arm64/mm/gcs.c | 8 ++++---- 3 files changed, 12 insertions(+), 12 deletions(-) diff --git a/arch/arm64/include/asm/gcs.h b/arch/arm64/include/asm/gcs.h index f50660603ecf..d8923b5f03b7 100644 --- a/arch/arm64/include/asm/gcs.h +++ b/arch/arm64/include/asm/gcs.h @@ -64,8 +64,8 @@ static inline bool task_gcs_el0_enabled(struct task_struct *task) void gcs_set_el0_mode(struct task_struct *task); void gcs_free(struct task_struct *task); void gcs_preserve_current_state(void); -unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, - const struct kernel_clone_args *args); +int gcs_alloc_thread_stack(struct task_struct *tsk, + const struct kernel_clone_args *args); static inline int gcs_check_locked(struct task_struct *task, unsigned long new_val) @@ -91,8 +91,8 @@ static inline bool task_gcs_el0_enabled(struct task_struct *task) static inline void gcs_set_el0_mode(struct task_struct *task) { } static inline void gcs_free(struct task_struct *task) { } static inline void gcs_preserve_current_state(void) { } -static inline unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, - const struct kernel_clone_args *args) +static inline int gcs_alloc_thread_stack(struct task_struct *tsk, + const struct kernel_clone_args *args) { return -ENOTSUPP; } diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 42faebb7b712..45130ea7ea6e 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -297,7 +297,7 @@ static void flush_gcs(void) static int copy_thread_gcs(struct task_struct *p, const struct kernel_clone_args *args) { - unsigned long gcs; + int ret; if (!system_supports_gcs()) return 0; @@ -305,9 +305,9 @@ static int copy_thread_gcs(struct task_struct *p, p->thread.gcs_base = 0; p->thread.gcs_size = 0; - gcs = gcs_alloc_thread_stack(p, args); - if (IS_ERR_VALUE(gcs)) - return PTR_ERR((void *)gcs); + ret = gcs_alloc_thread_stack(p, args); + if (ret != 0) + return ret; p->thread.gcs_el0_mode = current->thread.gcs_el0_mode; p->thread.gcs_el0_locked = current->thread.gcs_el0_locked; diff --git a/arch/arm64/mm/gcs.c b/arch/arm64/mm/gcs.c index 5c46ec527b1c..1f633a482558 100644 --- a/arch/arm64/mm/gcs.c +++ b/arch/arm64/mm/gcs.c @@ -38,8 +38,8 @@ static unsigned long gcs_size(unsigned long size) return max(PAGE_SIZE, size); } -unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, - const struct kernel_clone_args *args) +int gcs_alloc_thread_stack(struct task_struct *tsk, + const struct kernel_clone_args *args) { unsigned long addr, size; @@ -59,13 +59,13 @@ unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, size = gcs_size(size); addr = alloc_gcs(0, size); if (IS_ERR_VALUE(addr)) - return addr; + return PTR_ERR((void *)addr); tsk->thread.gcs_base = addr; tsk->thread.gcs_size = size; tsk->thread.gcspr_el0 = addr + size - sizeof(u64); - return addr; + return 0; } SYSCALL_DEFINE3(map_shadow_stack, unsigned long, addr, unsigned long, size, unsigned int, flags) From patchwork Tue Apr 8 18:49:42 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 879208 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C23F2241678; 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dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="J0X8XZX6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99D33C4CEE8; Tue, 8 Apr 2025 18:50:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744138239; bh=k56u8xsssiS9PLGw09HLQ5Vh+FXmTGCSWgKOA+mivOY=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=J0X8XZX61BVSHHOroz19lUhgfLNDjFWUqoEPUHRgjq7sZRsryzbd14wW/jwSyu9oQ F4kPGG9RJMWhIB6s3A/ZH2dJKpSJdZcBuewmrtk4iwPyDIoA8ExigjWRcst/gNymy5 Z9cBRUxvj5pTjyT1HdsVbFAjCUIjiizr6EwCywmt2oAOBj5sQLxegdg/2LJXqBoe5j z3f8f4Z2w7hWIZYB/K7pyguqXr5cdvQKAZcNrhQC2fwVO5SjJMmxYFa41P7aMnCsgM OyiJCJasBL5miT4eBoFJdb/ngL4MHeDwDh02f6pGYsfHccJIQYJI8j+WUlS5eZCU7Z R2z9k9BbeOpmA== From: Mark Brown Date: Tue, 08 Apr 2025 19:49:42 +0100 Subject: [PATCH RFT v15 2/8] Documentation: userspace-api: Add shadow stack API documentation Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250408-clone3-shadow-stack-v15-2-3fa245c6e3be@kernel.org> References: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> In-Reply-To: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-c25d1 X-Developer-Signature: v=1; a=openpgp-sha256; l=3235; i=broonie@kernel.org; h=from:subject:message-id; bh=k56u8xsssiS9PLGw09HLQ5Vh+FXmTGCSWgKOA+mivOY=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn9W/ooniTARt6/JF4hCBA0D+hWJCBXdE+dR3uxruN RVcDO7uJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ/Vv6AAKCRAk1otyXVSH0OO1B/ 9Srn6gXti+dRcHL9KQNBljGQUtUQRC2oVqUsr/DjwQo0+mm6HdNnrMT3HLRZklF/1XLe0cS+h2koMF +UGWiuriCRQqyffiIA4wGW7KpxvGd7hESCAwmQ/C7mhQpisDaJZt1XJiXuj8bofn1kqzrzIHvTfHm6 U8NlJGDWYbc9BXJKMJMkg5jRTgPPJwztgog8l2m02J9mJScJBLkwfRDRrETpKRuk/dX/Pqc4K54WFh OWF86/phmJPUitNJXumc68mYfXhSMecwScRFCjWWYTMiLdHpRPu22riHXQ1e1+9LOVhXPKrF7+slw3 fljMC7En+Qif/nkg+9qT2lYvbyx3Xu X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB There are a number of architectures with shadow stack features which we are presenting to userspace with as consistent an API as we can (though there are some architecture specifics). Especially given that there are some important considerations for userspace code interacting directly with the feature let's provide some documentation covering the common aspects. Reviewed-by: Catalin Marinas Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Acked-by: Yury Khrustalev Reviewed-by: Deepak Gupta Signed-off-by: Mark Brown --- Documentation/userspace-api/index.rst | 1 + Documentation/userspace-api/shadow_stack.rst | 44 ++++++++++++++++++++++++++++ 2 files changed, 45 insertions(+) diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst index b8c73be4fb11..0167e59b541e 100644 --- a/Documentation/userspace-api/index.rst +++ b/Documentation/userspace-api/index.rst @@ -62,6 +62,7 @@ Everything else ELF netlink/index + shadow_stack sysfs-platform_profile vduse futex2 diff --git a/Documentation/userspace-api/shadow_stack.rst b/Documentation/userspace-api/shadow_stack.rst new file mode 100644 index 000000000000..65c665496624 --- /dev/null +++ b/Documentation/userspace-api/shadow_stack.rst @@ -0,0 +1,44 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============= +Shadow Stacks +============= + +Introduction +============ + +Several architectures have features which provide backward edge +control flow protection through a hardware maintained stack, only +writeable by userspace through very limited operations. This feature +is referred to as shadow stacks on Linux, on x86 it is part of Intel +Control Enforcement Technology (CET), on arm64 it is Guarded Control +Stacks feature (FEAT_GCS) and for RISC-V it is the Zicfiss extension. +It is expected that this feature will normally be managed by the +system dynamic linker and libc in ways broadly transparent to +application code, this document covers interfaces and considerations. + + +Enabling +======== + +Shadow stacks default to disabled when a userspace process is +executed, they can be enabled for the current thread with a syscall: + + - For x86 the ARCH_SHSTK_ENABLE arch_prctl() + - For other architectures the PR_SET_SHADOW_STACK_ENABLE prctl() + +It is expected that this will normally be done by the dynamic linker. +Any new threads created by a thread with shadow stacks enabled will +themselves have shadow stacks enabled. + + +Enablement considerations +========================= + +- Returning from the function that enables shadow stacks without first + disabling them will cause a shadow stack exception. This includes + any syscall wrapper or other library functions, the syscall will need + to be inlined. +- A lock feature allows userspace to prevent disabling of shadow stacks. +- Those that change the stack context like longjmp() or use of ucontext + changes on signal return will need support from libc. From patchwork Tue Apr 8 18:49:43 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 879489 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D0D93230BF9; Tue, 8 Apr 2025 18:50:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744138246; cv=none; b=I98u9o9vyKNrRsmgSzzmozONhAXW8xh63BDN+Pv8yfnc89+iJ2jMgTGafcTAuwr3A8yS3rjMbhRqLxOqNeXUsOC8VtoIfsHUGFlnYRZcek6lcayJWTA8urkmv3gSKLA9rStHy/PNLtQPvrEQWoxL/WmXQbf5b3dAyb7Sx6X8Cl0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744138246; c=relaxed/simple; bh=8PwV5sD24lytiIg6Et3XNYcReWmnPu0HQVBivsfh4Ks=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=L2+KKVuyMml0FeMHGw4E5oMQp4QPz5iULTaSasY/88Tcdv26D8Kj+tAWsC2rExvhVZoZ+ihdeAXIS9+oTfqISB6n3BIqWNytdZLa1sdvSTGHHtuf1cIs4lkOvdA8Nb/G1i630kzjX9g3hij8X3/CByn8e2Nnx3dF0/bjwK1LgVY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=p4KmfBUN; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="p4KmfBUN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A5047C4CEE9; Tue, 8 Apr 2025 18:50:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744138245; bh=8PwV5sD24lytiIg6Et3XNYcReWmnPu0HQVBivsfh4Ks=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=p4KmfBUNE71JkEA0k8dGAISxj8C8if/JKK5Z4mxa28fGXU4nt5MjJ9cx7B8iO25MK HXffqdnQLXG39AO/ULchptTKqWCsnvy3T9x2FZ8SyyFbmKp4806U6Lb5XseJBb9EHI Y26Ax8wFDWv6NdtMn1ZiyJ2kRIxUlPcNcsoukhHMtNOlF7Gw93re/nmvnM1RxWklWR vJMTDku76DNr6/tTj0t8n9sedMcLd+15znLZoeWRJaT7hOwtWWGUuShLWNAZURVPtx ARkkFuZTFen51CWBlyCXuCTy1TOCH3X8QU/aIAsPXtPS1zylDE4fq8Zdwk1r+gbD8m f2sa5CvWcHuZw== From: Mark Brown Date: Tue, 08 Apr 2025 19:49:43 +0100 Subject: [PATCH RFT v15 3/8] selftests: Provide helper header for shadow stack testing Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250408-clone3-shadow-stack-v15-3-3fa245c6e3be@kernel.org> References: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> In-Reply-To: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-c25d1 X-Developer-Signature: v=1; a=openpgp-sha256; l=4329; i=broonie@kernel.org; h=from:subject:message-id; bh=8PwV5sD24lytiIg6Et3XNYcReWmnPu0HQVBivsfh4Ks=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn9W/oQj317ibp/NHMl71NrO9hKviKUy4s+msy2j+5 6p7QQ3GJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ/Vv6AAKCRAk1otyXVSH0FYKCA CC7dERQqiJ26ze1jtYlzO56eQRr7IPuE364X3G9FheZcqPzBx/fI4b8i0TkZP+Xsh54gc1GmdS6/2A 36Uon1rDfqoKf+UWJoYLdfk+GzhACRVcqhf6AdJTiL5XD2CGB5XI7BwsVXIY2QkmnlDpqqmOQAYKbd ru1RdLPePcsMCi4t4eBzwOyUoZXTeJdvzVTWzENiyKiZviXjrJeLCJdsBFTL1x7/IxOrU5dobiotNr HqC+d03LS11sSXeVFcgnHVu5k0hdQw+1e50sUzFCCxAfODiUgTod4QjoX33jPWCfLEBlBhFiMhsYAl jJA/ZT2ZZ1+2pCH866rTLJSAWbpVQK X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB While almost all users of shadow stacks should be relying on the dynamic linker and libc to enable the feature there are several low level test programs where it is useful to enable without any libc support, allowing testing without full system enablement. This low level testing is helpful during bringup of the support itself, and also in enabling coverage by automated testing without needing all system components in the target root filesystems to have enablement. Provide a header with helpers for this purpose, intended for use only by test programs directly exercising shadow stack interfaces. Reviewed-by: Rick Edgecombe Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Signed-off-by: Mark Brown --- tools/testing/selftests/ksft_shstk.h | 98 ++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) diff --git a/tools/testing/selftests/ksft_shstk.h b/tools/testing/selftests/ksft_shstk.h new file mode 100644 index 000000000000..fecf91218ea5 --- /dev/null +++ b/tools/testing/selftests/ksft_shstk.h @@ -0,0 +1,98 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Helpers for shadow stack enablement, this is intended to only be + * used by low level test programs directly exercising interfaces for + * working with shadow stacks. + * + * Copyright (C) 2024 ARM Ltd. + */ + +#ifndef __KSFT_SHSTK_H +#define __KSFT_SHSTK_H + +#include + +/* This is currently only defined for x86 */ +#ifndef SHADOW_STACK_SET_TOKEN +#define SHADOW_STACK_SET_TOKEN (1ULL << 0) +#endif + +static bool shadow_stack_enabled; + +#ifdef __x86_64__ +#define ARCH_SHSTK_ENABLE 0x5001 +#define ARCH_SHSTK_SHSTK (1ULL << 0) + +#define ARCH_PRCTL(arg1, arg2) \ +({ \ + long _ret; \ + register long _num asm("eax") = __NR_arch_prctl; \ + register long _arg1 asm("rdi") = (long)(arg1); \ + register long _arg2 asm("rsi") = (long)(arg2); \ + \ + asm volatile ( \ + "syscall\n" \ + : "=a"(_ret) \ + : "r"(_arg1), "r"(_arg2), \ + "0"(_num) \ + : "rcx", "r11", "memory", "cc" \ + ); \ + _ret; \ +}) + +#define ENABLE_SHADOW_STACK +static __always_inline void enable_shadow_stack(void) +{ + int ret = ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK); + if (ret == 0) + shadow_stack_enabled = true; +} + +#endif + +#ifdef __aarch64__ +#define PR_SET_SHADOW_STACK_STATUS 75 +# define PR_SHADOW_STACK_ENABLE (1UL << 0) + +#define my_syscall2(num, arg1, arg2) \ +({ \ + register long _num __asm__ ("x8") = (num); \ + register long _arg1 __asm__ ("x0") = (long)(arg1); \ + register long _arg2 __asm__ ("x1") = (long)(arg2); \ + register long _arg3 __asm__ ("x2") = 0; \ + register long _arg4 __asm__ ("x3") = 0; \ + register long _arg5 __asm__ ("x4") = 0; \ + \ + __asm__ volatile ( \ + "svc #0\n" \ + : "=r"(_arg1) \ + : "r"(_arg1), "r"(_arg2), \ + "r"(_arg3), "r"(_arg4), \ + "r"(_arg5), "r"(_num) \ + : "memory", "cc" \ + ); \ + _arg1; \ +}) + +#define ENABLE_SHADOW_STACK +static __always_inline void enable_shadow_stack(void) +{ + int ret; + + ret = my_syscall2(__NR_prctl, PR_SET_SHADOW_STACK_STATUS, + PR_SHADOW_STACK_ENABLE); + if (ret == 0) + shadow_stack_enabled = true; +} + +#endif + +#ifndef __NR_map_shadow_stack +#define __NR_map_shadow_stack 453 +#endif + +#ifndef ENABLE_SHADOW_STACK +static inline void enable_shadow_stack(void) { } +#endif + +#endif From patchwork Tue Apr 8 18:49:44 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 879207 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 65D68230BF9; Tue, 8 Apr 2025 18:50:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; 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Tue, 8 Apr 2025 18:50:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744138251; bh=7mJGjuxOFb+EcNlOifyGFZevkI7TG3oJ1zx+/DiPMPU=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=e0v/5CvzDmaquTQObQpk7Vd7hZvndgLS4I5ffFrFfnE6Q7EkaMXmpwhv1rzhf/Cds ubhgZg9eEqJ9n/sgAWX1NyNPMnObflAiJIp+qWgVyVl+2xngnH0noXP43iVyLQMAwP AkhLQS7QAqFJhVQeqnRbVLSSIiDwEIZzRttW0R4JdxMztAelWko1U3hMMqWnv1JLk5 eUUbEZe5e/zQoKEs1YH80LOMuZqZIQFZ+CjdWzfiOI4nrFVZpqfCa2Ky8Aav1h2nIq HAAz9rlt1jpanysDO1J7LHsCO80e3LojsvOdpTuDPBAm0pudsA74wQz9RR/cQFYg/y 1tpXSztmvyMTg== From: Mark Brown Date: Tue, 08 Apr 2025 19:49:44 +0100 Subject: [PATCH RFT v15 4/8] fork: Add shadow stack support to clone3() Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250408-clone3-shadow-stack-v15-4-3fa245c6e3be@kernel.org> References: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> In-Reply-To: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook X-Mailer: b4 0.15-dev-c25d1 X-Developer-Signature: v=1; a=openpgp-sha256; l=16376; i=broonie@kernel.org; h=from:subject:message-id; bh=7mJGjuxOFb+EcNlOifyGFZevkI7TG3oJ1zx+/DiPMPU=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn9W/pGevJ5DQyFLSgCkQQbsS2nCAAs88VjO64CYNx aTVnNF6JATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ/Vv6QAKCRAk1otyXVSH0EgZB/ 9JA7WGFaAmZ5YtMfVrwSrjbwYRItPxi9Qj/c6fMmqdlmneaar0Bn5sksNKgmXyckNHCrwGbW3D8jN5 qogxY0L4qoTkwLSAxbBdXaX+J8Q1k47oABP5jRT4uFDOWDMQDKySRfHHbu0igi1GKbXSGJLl6MxzCh /+y8/74UABCCBGi2OFKr8H0sU0GXOmy8arFWqdzqi62URMXJkyPymVaNAVuZg80lGnIbxt8tsk0J0G HY2jUIEm/dJjnkb3xPCZ7qr6VQf5n9uwJKd7cI33LBt8WqfQrNobl3mwUHRDgK0GVcan9q/vYRStGj fxCu2ObyXODVgFpOYe2hEDiGv/EypW X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Unlike with the normal stack there is no API for configuring the shadow stack for a new thread, instead the kernel will dynamically allocate a new shadow stack with the same size as the normal stack. This appears to be due to the shadow stack series having been in development since before the more extensible clone3() was added rather than anything more deliberate. Add a parameter to clone3() specifying the shadow stack pointer to use for the new thread, this is inconsistent with the way we specify the normal stack but during review concerns were expressed about having to identify where the shadow stack pointer should be placed especially in cases where the shadow stack has been previously active. If no shadow stack is specified then the existing implicit allocation behaviour is maintained. If a shadow stack pointer is specified then it is required to have an architecture defined token placed on the stack, this will be consumed by the new task. If no valid token is present then this will be reported with -EINVAL. This token prevents new threads being created pointing at the shadow stack of an existing running thread. If the architecture does not support shadow stacks the shadow stack pointer must be not be specified, architectures that do support the feature are expected to enforce the same requirement on individual systems that lack shadow stack support. Update the existing arm64 and x86 implementations to pay attention to the newly added arguments, in order to maintain compatibility we use the existing behaviour if no shadow stack is specified. Since we are now using more fields from the kernel_clone_args we pass that into the shadow stack code rather than individual fields. Portions of the x86 architecture code were written by Rick Edgecombe. Acked-by: Yury Khrustalev Signed-off-by: Mark Brown --- arch/arm64/mm/gcs.c | 54 +++++++++++++++++++++- arch/x86/include/asm/shstk.h | 11 +++-- arch/x86/kernel/process.c | 2 +- arch/x86/kernel/shstk.c | 57 +++++++++++++++++++++--- include/asm-generic/cacheflush.h | 11 +++++ include/linux/sched/task.h | 17 +++++++ include/uapi/linux/sched.h | 10 +++-- kernel/fork.c | 96 +++++++++++++++++++++++++++++++++++----- 8 files changed, 232 insertions(+), 26 deletions(-) diff --git a/arch/arm64/mm/gcs.c b/arch/arm64/mm/gcs.c index 1f633a482558..10ee92390ea1 100644 --- a/arch/arm64/mm/gcs.c +++ b/arch/arm64/mm/gcs.c @@ -43,8 +43,24 @@ int gcs_alloc_thread_stack(struct task_struct *tsk, { unsigned long addr, size; - if (!system_supports_gcs()) + if (!system_supports_gcs()) { + if (args->shadow_stack_pointer) + return -EINVAL; + + return 0; + } + + /* + * If the user specified a GCS then use it, otherwise fall + * back to a default allocation strategy. Validation is done + * in arch_shstk_validate_clone(). + */ + if (args->shadow_stack_pointer) { + tsk->thread.gcs_base = 0; + tsk->thread.gcs_size = 0; + tsk->thread.gcspr_el0 = args->shadow_stack_pointer; return 0; + } if (!task_gcs_el0_enabled(tsk)) return 0; @@ -68,6 +84,42 @@ int gcs_alloc_thread_stack(struct task_struct *tsk, return 0; } +static bool gcs_consume_token(struct vm_area_struct *vma, struct page *page, + unsigned long user_addr) +{ + u64 expected = GCS_CAP(user_addr); + u64 *token = page_address(page) + offset_in_page(user_addr); + + if (!cmpxchg_to_user_page(vma, page, user_addr, token, expected, 0)) + return false; + set_page_dirty_lock(page); + + return true; +} + +int arch_shstk_validate_clone(struct task_struct *tsk, + struct vm_area_struct *vma, + struct page *page, + struct kernel_clone_args *args) +{ + unsigned long gcspr_el0; + int ret = 0; + + /* Ensure that a token written as a result of a pivot is visible */ + gcsb_dsync(); + + gcspr_el0 = args->shadow_stack_pointer; + if (!gcs_consume_token(vma, page, gcspr_el0)) + return -EINVAL; + + tsk->thread.gcspr_el0 = gcspr_el0 + sizeof(u64); + + /* Ensure that our token consumption visible */ + gcsb_dsync(); + + return ret; +} + SYSCALL_DEFINE3(map_shadow_stack, unsigned long, addr, unsigned long, size, unsigned int, flags) { unsigned long alloc_size; diff --git a/arch/x86/include/asm/shstk.h b/arch/x86/include/asm/shstk.h index ba6f2fe43848..827e983430aa 100644 --- a/arch/x86/include/asm/shstk.h +++ b/arch/x86/include/asm/shstk.h @@ -6,6 +6,7 @@ #include struct task_struct; +struct kernel_clone_args; struct ksignal; #ifdef CONFIG_X86_USER_SHADOW_STACK @@ -16,8 +17,8 @@ struct thread_shstk { long shstk_prctl(struct task_struct *task, int option, unsigned long arg2); void reset_thread_features(void); -unsigned long shstk_alloc_thread_stack(struct task_struct *p, unsigned long clone_flags, - unsigned long stack_size); +unsigned long shstk_alloc_thread_stack(struct task_struct *p, + const struct kernel_clone_args *args); void shstk_free(struct task_struct *p); int setup_signal_shadow_stack(struct ksignal *ksig); int restore_signal_shadow_stack(void); @@ -28,8 +29,10 @@ static inline long shstk_prctl(struct task_struct *task, int option, unsigned long arg2) { return -EINVAL; } static inline void reset_thread_features(void) {} static inline unsigned long shstk_alloc_thread_stack(struct task_struct *p, - unsigned long clone_flags, - unsigned long stack_size) { return 0; } + const struct kernel_clone_args *args) +{ + return 0; +} static inline void shstk_free(struct task_struct *p) {} static inline int setup_signal_shadow_stack(struct ksignal *ksig) { return 0; } static inline int restore_signal_shadow_stack(void) { return 0; } diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 962c3ce39323..002b05483c62 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -213,7 +213,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) * is disabled, new_ssp will remain 0, and fpu_clone() will know not to * update it. */ - new_ssp = shstk_alloc_thread_stack(p, clone_flags, args->stack_size); + new_ssp = shstk_alloc_thread_stack(p, args); if (IS_ERR_VALUE(new_ssp)) return PTR_ERR((void *)new_ssp); diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c index 059685612362..056e2c9ec305 100644 --- a/arch/x86/kernel/shstk.c +++ b/arch/x86/kernel/shstk.c @@ -191,18 +191,65 @@ void reset_thread_features(void) current->thread.features_locked = 0; } -unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long clone_flags, - unsigned long stack_size) +int arch_shstk_validate_clone(struct task_struct *t, + struct vm_area_struct *vma, + struct page *page, + struct kernel_clone_args *args) +{ + /* + * SSP is aligned, so reserved bits and mode bit are a zero, just mark + * the token 64-bit. + */ + void *maddr = kmap_local_page(page); + int offset; + unsigned long addr, ssp; + u64 expected; + + if (!features_enabled(ARCH_SHSTK_SHSTK)) + return 0; + + ssp = args->shadow_stack_pointer; + addr = ssp - SS_FRAME_SIZE; + expected = ssp | BIT(0); + offset = offset_in_page(addr); + + if (!cmpxchg_to_user_page(vma, page, addr, (unsigned long *)(maddr + offset), + expected, 0)) + return -EINVAL; + set_page_dirty_lock(page); + + return 0; +} + +unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, + const struct kernel_clone_args *args) { struct thread_shstk *shstk = &tsk->thread.shstk; + unsigned long clone_flags = args->flags; unsigned long addr, size; /* * If shadow stack is not enabled on the new thread, skip any - * switch to a new shadow stack. + * implicit switch to a new shadow stack and reject attempts to + * explicitly specify one. */ - if (!features_enabled(ARCH_SHSTK_SHSTK)) + if (!features_enabled(ARCH_SHSTK_SHSTK)) { + if (args->shadow_stack_pointer) + return (unsigned long)ERR_PTR(-EINVAL); + return 0; + } + + /* + * If the user specified a shadow stack then use it, otherwise + * fall back to a default allocation strategy. Validation is + * done in arch_shstk_validate_clone(). + */ + if (args->shadow_stack_pointer) { + shstk->base = 0; + shstk->size = 0; + return args->shadow_stack_pointer; + } /* * For CLONE_VFORK the child will share the parents shadow stack. @@ -222,7 +269,7 @@ unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long cl if (!(clone_flags & CLONE_VM)) return 0; - size = adjust_shstk_size(stack_size); + size = adjust_shstk_size(args->stack_size); addr = alloc_shstk(0, size, 0, false); if (IS_ERR_VALUE(addr)) return addr; diff --git a/include/asm-generic/cacheflush.h b/include/asm-generic/cacheflush.h index 7ee8a179d103..96cc0c7a5c90 100644 --- a/include/asm-generic/cacheflush.h +++ b/include/asm-generic/cacheflush.h @@ -124,4 +124,15 @@ static inline void flush_cache_vunmap(unsigned long start, unsigned long end) } while (0) #endif +#ifndef cmpxchg_to_user_page +#define cmpxchg_to_user_page(vma, page, vaddr, ptr, old, new) \ +({ \ + bool ret; \ + \ + ret = try_cmpxchg(ptr, &old, new); \ + flush_icache_user_page(vma, page, vaddr, sizeof(*ptr)); \ + ret; \ +}) +#endif + #endif /* _ASM_GENERIC_CACHEFLUSH_H */ diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index ca1db4b92c32..5d1290f7d9c0 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -16,6 +16,7 @@ struct task_struct; struct rusage; union thread_union; struct css_set; +struct vm_area_struct; /* All the bits taken by the old clone syscall. */ #define CLONE_LEGACY_FLAGS 0xffffffffULL @@ -44,6 +45,7 @@ struct kernel_clone_args { struct cgroup *cgrp; struct css_set *cset; unsigned int kill_seq; + unsigned long shadow_stack_pointer; }; /* @@ -237,4 +239,19 @@ static inline void task_unlock(struct task_struct *p) DEFINE_GUARD(task_lock, struct task_struct *, task_lock(_T), task_unlock(_T)) +#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK +int arch_shstk_validate_clone(struct task_struct *p, + struct vm_area_struct *vma, + struct page *page, + struct kernel_clone_args *args); +#else +static inline int arch_shstk_validate_clone(struct task_struct *p, + struct vm_area_struct *vma, + struct page *page, + struct kernel_clone_args *args) +{ + return 0; +} +#endif + #endif /* _LINUX_SCHED_TASK_H */ diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h index 359a14cc76a4..586a1c05a4e4 100644 --- a/include/uapi/linux/sched.h +++ b/include/uapi/linux/sched.h @@ -84,6 +84,8 @@ * kernel's limit of nested PID namespaces. * @cgroup: If CLONE_INTO_CGROUP is specified set this to * a file descriptor for the cgroup. + * @shadow_stack_pointer: Value to use for shadow stack pointer in the + * child process. * * The structure is versioned by size and thus extensible. * New struct members must go at the end of the struct and @@ -101,12 +103,14 @@ struct clone_args { __aligned_u64 set_tid; __aligned_u64 set_tid_size; __aligned_u64 cgroup; + __aligned_u64 shadow_stack_pointer; }; #endif -#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */ -#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */ -#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */ +#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */ +#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */ +#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */ +#define CLONE_ARGS_SIZE_VER3 96 /* sizeof fourth published struct */ /* * Scheduling policies diff --git a/kernel/fork.c b/kernel/fork.c index c4b26cd8998b..a0427524fec3 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2162,6 +2162,51 @@ static void rv_task_fork(struct task_struct *p) #define rv_task_fork(p) do {} while (0) #endif +static int shstk_validate_clone(struct task_struct *p, + struct kernel_clone_args *args) +{ + struct mm_struct *mm; + struct vm_area_struct *vma; + struct page *page; + unsigned long addr; + int ret; + + if (!IS_ENABLED(CONFIG_ARCH_HAS_USER_SHADOW_STACK)) + return 0; + + if (!args->shadow_stack_pointer) + return 0; + + mm = get_task_mm(p); + if (!mm) + return -EFAULT; + + mmap_read_lock(mm); + + addr = untagged_addr_remote(mm, args->shadow_stack_pointer); + page = get_user_page_vma_remote(mm, addr, FOLL_FORCE | FOLL_WRITE, + &vma); + if (IS_ERR(page)) { + ret = -EFAULT; + goto out; + } + + if (!(vma->vm_flags & VM_SHADOW_STACK) || + !(vma->vm_flags & VM_WRITE)) { + ret = -EFAULT; + goto out_page; + } + + ret = arch_shstk_validate_clone(p, vma, page, args); + +out_page: + put_page(page); +out: + mmap_read_unlock(mm); + mmput(mm); + return ret; +} + /* * This creates a new process as a copy of the old one, * but does not actually start it yet. @@ -2436,6 +2481,9 @@ __latent_entropy struct task_struct *copy_process( if (retval) goto bad_fork_cleanup_namespaces; retval = copy_thread(p, args); + if (retval) + goto bad_fork_cleanup_io; + retval = shstk_validate_clone(p, args); if (retval) goto bad_fork_cleanup_io; @@ -3002,7 +3050,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, CLONE_ARGS_SIZE_VER1); BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) != CLONE_ARGS_SIZE_VER2); - BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2); + BUILD_BUG_ON(offsetofend(struct clone_args, shadow_stack_pointer) != + CLONE_ARGS_SIZE_VER3); + BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER3); if (unlikely(usize > PAGE_SIZE)) return -E2BIG; @@ -3035,16 +3085,17 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, return -EINVAL; *kargs = (struct kernel_clone_args){ - .flags = args.flags, - .pidfd = u64_to_user_ptr(args.pidfd), - .child_tid = u64_to_user_ptr(args.child_tid), - .parent_tid = u64_to_user_ptr(args.parent_tid), - .exit_signal = args.exit_signal, - .stack = args.stack, - .stack_size = args.stack_size, - .tls = args.tls, - .set_tid_size = args.set_tid_size, - .cgroup = args.cgroup, + .flags = args.flags, + .pidfd = u64_to_user_ptr(args.pidfd), + .child_tid = u64_to_user_ptr(args.child_tid), + .parent_tid = u64_to_user_ptr(args.parent_tid), + .exit_signal = args.exit_signal, + .stack = args.stack, + .stack_size = args.stack_size, + .tls = args.tls, + .set_tid_size = args.set_tid_size, + .cgroup = args.cgroup, + .shadow_stack_pointer = args.shadow_stack_pointer, }; if (args.set_tid && @@ -3085,6 +3136,27 @@ static inline bool clone3_stack_valid(struct kernel_clone_args *kargs) return true; } +/** + * clone3_shadow_stack_valid - check and prepare shadow stack + * @kargs: kernel clone args + * + * Verify that shadow stacks are only enabled if supported. + */ +static inline bool clone3_shadow_stack_valid(struct kernel_clone_args *kargs) +{ + if (!kargs->shadow_stack_pointer) + return true; + + if (!IS_ALIGNED(kargs->shadow_stack_pointer, sizeof(void *))) + return false; + + /* + * The architecture must check support on the specific + * machine. + */ + return IS_ENABLED(CONFIG_ARCH_HAS_USER_SHADOW_STACK); +} + static bool clone3_args_valid(struct kernel_clone_args *kargs) { /* Verify that no unknown flags are passed along. */ @@ -3107,7 +3179,7 @@ static bool clone3_args_valid(struct kernel_clone_args *kargs) kargs->exit_signal) return false; - if (!clone3_stack_valid(kargs)) + if (!clone3_stack_valid(kargs) || !clone3_shadow_stack_valid(kargs)) return false; return true; From patchwork Tue Apr 8 18:49:45 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 879488 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E8489230BF9; Tue, 8 Apr 2025 18:50:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744138258; cv=none; b=bcqV8VQIX8WSzCzN8zcIFKnuZyLZxqJ6GPuvv2Qq9TA5cwEO98eISgx0QWHcpECc5HZqg1MW0GJ8vpQLLSTak/6LG5oGmt0G0RwA/5X3vPHdVu5tNkg9MHxZKlZNxc+m9WMXsDO4k1+zWkjAy7mf+2kbsZ+KQIymi1wVucgh2cY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744138258; c=relaxed/simple; bh=/AYgqTLwHHsTkCX7TTH1Na+bth+vthYvgf8svHl0eTc=; 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Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-c25d1 X-Developer-Signature: v=1; a=openpgp-sha256; l=1114; i=broonie@kernel.org; h=from:subject:message-id; bh=/AYgqTLwHHsTkCX7TTH1Na+bth+vthYvgf8svHl0eTc=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn9W/qsXFcBmtSU2fNjqhpFuycLbaqHNAvW1e/ZFtL YsmbfIGJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ/Vv6gAKCRAk1otyXVSH0NE1B/ 9tlQB01aHygXB73eQ3RbIBxf74OCyit3DJw7CGC215xTJSlbRlFbG5hYR2CcQchUQoq5L8ObDN+LmY dJ7uBnlqstpslYhN6gUbs24WQrpDYjDm1IRqPenlPLWt1+WaSenGwbHDHB1vNW8bz31cmw+WiPaoIh +C5CXEBIgrHf3o6dTpdyP8aB4+E+vrE8dtwWZuV4JQgy3LXBDETtfPCL2lLx1CFPWkZF86GjnjaEf0 KaObT0c270s2pqyt8dnrAFs9ybHYg5HNdXkWTWYyCejn+ouvsrAAK3FY3shWSmnmY02vbWG4BZWfBa 34rQoJ9zBYts605lxt4Ym4Yh2jPd+G X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Since there were widespread issues with output not being flushed the kselftest framework was modified to explicitly set the output streams unbuffered in commit 58e2847ad2e6 ("selftests: line buffer test program's stdout") so there is no need to explicitly flush in the clone3 tests. Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Reviewed-by: Catalin Marinas Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3_selftests.h | 2 -- 1 file changed, 2 deletions(-) diff --git a/tools/testing/selftests/clone3/clone3_selftests.h b/tools/testing/selftests/clone3/clone3_selftests.h index eeca8005723f..939b26c86d42 100644 --- a/tools/testing/selftests/clone3/clone3_selftests.h +++ b/tools/testing/selftests/clone3/clone3_selftests.h @@ -35,8 +35,6 @@ struct __clone_args { static pid_t sys_clone3(struct __clone_args *args, size_t size) { - fflush(stdout); - fflush(stderr); return syscall(__NR_clone3, args, size); } From patchwork Tue Apr 8 18:49:46 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 879206 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 933A2256D; Tue, 8 Apr 2025 18:51:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744138263; cv=none; b=UQI1FY28HMTgPEtsG6jS/6doCi2MaxtEfes0nieO9/XdyGuT8fLmiswM7tYjXt1+lg0kchAtp3sdL1Q+qWANCz0ECq+NTY3qpCsorkC6zQpqGKHFxMeELJwhY9I/pVnJxUkKfA3BRFal4I7IAY1R1vMmZ5NVLhqC3vgWO6cwtGk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744138263; c=relaxed/simple; bh=1QQTqlYHUjewASmFh86Dd+jl+m64vZGkDAeB+lVVa3I=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=JtYoJ4kolZrabbrNAz2GSGkA4xOB42Zl8ztS2+34PMqeoC/1N2fEBF/A2Ed1xAKwS9v670BJ46pSg1dZd7doQE8RaRnHC/9PfBWlP6OAiwmncdUZy0UtxwXy4fJCDu6NRvgacudQejM3Yd1+Raik50wOBJHm+Fx1gaHUI4Draj4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=tVEz1zcD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="tVEz1zcD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C6D46C4CEED; Tue, 8 Apr 2025 18:50:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744138263; bh=1QQTqlYHUjewASmFh86Dd+jl+m64vZGkDAeB+lVVa3I=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=tVEz1zcDAjlOjs/RHoMZ0E+olCncmQ+1E8mXBntv6H4X0xRZmYt/F9clZr0wzwyU8 V6NKLHxy+aXVTE4qB7UQggTNpKn48LV9kL5caiVcDsysXkNhjjRZvexi3Ucb8z8Hrc nkSq7Z9X+2g4vxACSWtQjFLrU6CAjFRSBr+8yPFcrFKTs05Rz+F5Lty5n1hg+JykaS A0geMBmRWBTAdPOrzGihT4ooMdPm2QI3PfPFu1d4kPFYODAoDfU/rRCrgNHrwYG1D7 V5GYx9oXAlam47v/ELwPexLb+U8z/D5EfsC9oHNm97nz8JsrEy9wC+0kiq1TL4s527 5irvTNVINsCNQ== From: Mark Brown Date: Tue, 08 Apr 2025 19:49:46 +0100 Subject: [PATCH RFT v15 6/8] selftests/clone3: Factor more of main loop into test_clone3() Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250408-clone3-shadow-stack-v15-6-3fa245c6e3be@kernel.org> References: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> In-Reply-To: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-c25d1 X-Developer-Signature: v=1; a=openpgp-sha256; l=3931; i=broonie@kernel.org; h=from:subject:message-id; bh=1QQTqlYHUjewASmFh86Dd+jl+m64vZGkDAeB+lVVa3I=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn9W/r1Mr2S49RxTacwu4TSa0qgbUe8fMzqooomHJp /z5UPSGJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ/Vv6wAKCRAk1otyXVSH0NevB/ 91VS1MjIA+aUqIzW3eazJxkOw6xK8bNbjoc8cFPt/LrnEAIEnifcXmIKgVP9498Ztd8q1v09F+s984 qrELmfjMpIUSoGYam5pjzU/MCL0OCa39rRoU14MMTr3/REsubp16GrWJJcyxZBU9ZuDBNo166/2Sl+ NtelrcjqmqsLx2VcWZdGuG/yPHgtPlwesCYIcXfiac4R4VMUrEyMt8m4d1EsSg44YP4C0/skG4DR3o Dz9g5IcxMc1pno2Ok8Eqodx4b5gPGFRBie6j49BB160qwc8NrE2Z4JWVQT17lV/G9Zz8IAof23XcN1 bJ6KcGn9W0VXwZOj7S4oxXKGDoBwRe X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB In order to make it easier to add more configuration for the tests and more support for runtime detection of when tests can be run pass the structure describing the tests into test_clone3() rather than picking the arguments out of it and have that function do all the per-test work. No functional change. Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Reviewed-by: Catalin Marinas Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3.c | 77 ++++++++++++++++----------------- 1 file changed, 37 insertions(+), 40 deletions(-) diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c index e61f07973ce5..e066b201fa64 100644 --- a/tools/testing/selftests/clone3/clone3.c +++ b/tools/testing/selftests/clone3/clone3.c @@ -30,6 +30,19 @@ enum test_mode { CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG, }; +typedef bool (*filter_function)(void); +typedef size_t (*size_function)(void); + +struct test { + const char *name; + uint64_t flags; + size_t size; + size_function size_function; + int expected; + enum test_mode test_mode; + filter_function filter; +}; + static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) { struct __clone_args args = { @@ -109,30 +122,40 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) return 0; } -static bool test_clone3(uint64_t flags, size_t size, int expected, - enum test_mode test_mode) +static void test_clone3(const struct test *test) { + size_t size; int ret; + if (test->filter && test->filter()) { + ksft_test_result_skip("%s\n", test->name); + return; + } + + if (test->size_function) + size = test->size_function(); + else + size = test->size; + + ksft_print_msg("Running test '%s'\n", test->name); + ksft_print_msg( "[%d] Trying clone3() with flags %#" PRIx64 " (size %zu)\n", - getpid(), flags, size); - ret = call_clone3(flags, size, test_mode); + getpid(), test->flags, size); + ret = call_clone3(test->flags, size, test->test_mode); ksft_print_msg("[%d] clone3() with flags says: %d expected %d\n", - getpid(), ret, expected); - if (ret != expected) { + getpid(), ret, test->expected); + if (ret != test->expected) { ksft_print_msg( "[%d] Result (%d) is different than expected (%d)\n", - getpid(), ret, expected); - return false; + getpid(), ret, test->expected); + ksft_test_result_fail("%s\n", test->name); + return; } - return true; + ksft_test_result_pass("%s\n", test->name); } -typedef bool (*filter_function)(void); -typedef size_t (*size_function)(void); - static bool not_root(void) { if (getuid() != 0) { @@ -160,16 +183,6 @@ static size_t page_size_plus_8(void) return getpagesize() + 8; } -struct test { - const char *name; - uint64_t flags; - size_t size; - size_function size_function; - int expected; - enum test_mode test_mode; - filter_function filter; -}; - static const struct test tests[] = { { .name = "simple clone3()", @@ -319,24 +332,8 @@ int main(int argc, char *argv[]) ksft_set_plan(ARRAY_SIZE(tests)); test_clone3_supported(); - for (i = 0; i < ARRAY_SIZE(tests); i++) { - if (tests[i].filter && tests[i].filter()) { - ksft_test_result_skip("%s\n", tests[i].name); - continue; - } - - if (tests[i].size_function) - size = tests[i].size_function(); - else - size = tests[i].size; - - ksft_print_msg("Running test '%s'\n", tests[i].name); - - ksft_test_result(test_clone3(tests[i].flags, size, - tests[i].expected, - tests[i].test_mode), - "%s\n", tests[i].name); - } + for (i = 0; i < ARRAY_SIZE(tests); i++) + test_clone3(&tests[i]); ksft_finished(); } From patchwork Tue Apr 8 18:49:47 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 879487 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5E89D24290F; Tue, 8 Apr 2025 18:51:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744138272; cv=none; b=ZqXydFJTNtv2NVqSIQqXIVECoD3PQF0x0JeHntIgvlOOaMxyFYNOTvlRFrP/VKvn4E0dOux9Q7IsAI14wA3uyGnzzEMLS3NRY8sqaZ0MTMUKSrgDX7/hP83SwbZp2CdGWPTrkLqx6lluXHjAvc6ZfFsBCPIv6zxuee6aWpphupM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744138272; c=relaxed/simple; bh=58+3HJOajqHhaBuOa7ipEd3ah9IrK8/b0nQffaXKgLE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=qnjTwN90qYI+T1PkMIROd9Yv7WTI/Jq8WJXlrMkHK3z0VcTOkq/XoFSta6y2HOUI5PYoXMIcuAZHrD2YQSjYzvp72KLUC+bki0KhxdEvyMHqMBbgnY9zQ0GDSoKpWxhqcbmzbG+SbVr5MK+0MWzWOTP71wNCnlMUyASOCKCPhGs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gSUBVb/F; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gSUBVb/F" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DF77DC4CEE8; Tue, 8 Apr 2025 18:51:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744138271; bh=58+3HJOajqHhaBuOa7ipEd3ah9IrK8/b0nQffaXKgLE=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=gSUBVb/F1PN9ub4RGkOs3bcYYUXZSF4KKDRLTPsa6tY/7hN5Vk/9zvZeg1v+UV8E9 fRNf3hTDqkSGed28QNcvNoPUQsC/Zk6n8DxgTixcE1HTTgzcQ8WgiqzDpv7qeto6CR LHuAkaUi7Fi7d9cmVGbVOv2yS9byjGibO+kKr0BiyrkmtwRtrcr91WlAC0J0YAij0C y/U69qzK4nEa6+y0PetK7+Jb5glrRdSmTzJAhMhO8041kSDzwoMRAaPsH0kAJIW18L 9vlz9OxSwMHL9DRpCEcnb7GrCsbOUljrIqTv5Ud0b5ystvumXnC1qc6u7tUVVzsb+z +9kdIVh8DpzGA== From: Mark Brown Date: Tue, 08 Apr 2025 19:49:47 +0100 Subject: [PATCH RFT v15 7/8] selftests/clone3: Allow tests to flag if -E2BIG is a valid error code Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250408-clone3-shadow-stack-v15-7-3fa245c6e3be@kernel.org> References: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> In-Reply-To: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-c25d1 X-Developer-Signature: v=1; a=openpgp-sha256; l=2075; i=broonie@kernel.org; h=from:subject:message-id; bh=58+3HJOajqHhaBuOa7ipEd3ah9IrK8/b0nQffaXKgLE=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn9W/rzEXC8qaSvjynqhm0QUrtxc5lFCc5P7cnVQYe ZsKOru2JATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ/Vv6wAKCRAk1otyXVSH0Ok7B/ 9npPrGfpneWB4nGE0oaFH6NX67+HHUx25iuZ4gd+y3vn2qwswOsu+2AwvgNUkdchV/ZCd4wLHtLGOk jGntNKx75rG5G02q6l3vHHjXPT0CQ44+IMdsY41jBUCmxcGuXpZ5UkSKWYK36+YZKi/EKJePEugyNd d9OxYYAtXU2mMQL7SiiBwqZeQK+tRAXbwDEo7YxhikMiwj0iducYIrAKeXGEgat779aTLPmbYiffQN Y5Wb0Zxao4+iuM+6p9OmSRvCTb/nKKXGCLApwFgQxkKaMF4ffGzJcOyR2SPeZR0Yp+kF/pKMT0NYdz 9VcVv9IN+/ZorSHqTinZXXOu/o30EY X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB The clone_args structure is extensible, with the syscall passing in the length of the structure. Inside the kernel we use copy_struct_from_user() to read the struct but this has the unfortunate side effect of silently accepting some overrun in the structure size providing the extra data is all zeros. This means that we can't discover the clone3() features that the running kernel supports by simply probing with various struct sizes. We need to check this for the benefit of test systems which run newer kselftests on old kernels. Add a flag which can be set on a test to indicate that clone3() may return -E2BIG due to the use of newer struct versions. Currently no tests need this but it will become an issue for testing clone3() support for shadow stacks, the support for shadow stacks is already present on x86. Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Reviewed-by: Catalin Marinas Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c index e066b201fa64..5b8b7d640e70 100644 --- a/tools/testing/selftests/clone3/clone3.c +++ b/tools/testing/selftests/clone3/clone3.c @@ -39,6 +39,7 @@ struct test { size_t size; size_function size_function; int expected; + bool e2big_valid; enum test_mode test_mode; filter_function filter; }; @@ -146,6 +147,11 @@ static void test_clone3(const struct test *test) ksft_print_msg("[%d] clone3() with flags says: %d expected %d\n", getpid(), ret, test->expected); if (ret != test->expected) { + if (test->e2big_valid && ret == -E2BIG) { + ksft_print_msg("Test reported -E2BIG\n"); + ksft_test_result_skip("%s\n", test->name); + return; + } ksft_print_msg( "[%d] Result (%d) is different than expected (%d)\n", getpid(), ret, test->expected); From patchwork Tue Apr 8 18:49:48 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 879205 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 582C01CB501; Tue, 8 Apr 2025 18:51:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744138279; cv=none; b=K/1RtilShN6KEXc9VIbrvSPmLVZCUsoOuFBHAgMM8crXfRH4f5OWhq6lT/8j+vB3SwsjjADJoBgAkZqNkrCBSrZxp9RkJd9wTMx31Zft41oKkV0BxoDXg+2ioGdJaTnwaEQJX2ol4UY5ogv7REbEylwwJn2pvxCQeRiyHU/fXyU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744138279; c=relaxed/simple; bh=5k3/QTD0kVCASnddHQWSmUjfH8nC3PpTtHcWbgjlz9A=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=DANIgHw5icYYxVS5LH5fcGTFi73KXwOvzjGrCqD/uIvXBarCycoP/RuAaHAKvn/AV86cN61coibxbEwUQIhcc9UzOAPARfM3A9B1Wo/H9RM7+muBx6AvsY5Sxc/hoL5aEwgnxlVjj9+VZzZiS8RkKCSWjLGk7TQ9+o139BD0ZOQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KAf8tBTF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KAf8tBTF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3F93AC4CEEA; Tue, 8 Apr 2025 18:51:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744138278; bh=5k3/QTD0kVCASnddHQWSmUjfH8nC3PpTtHcWbgjlz9A=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=KAf8tBTFIoMrIi3Ue5ivhB51gpnpXw4/rG9vlwIvcekDVG+SitT/bdClhJOdl0piv ln+cexaTiq/trh97WYUiocUywWEdR/0fQQDeRA+2GN92gVHZH1/kPojfKtoDFcwD8U sAcuRKdabGb9dDaTw/CukHoHU1n1OzQdQIxF7IyYSUSIBSHJxcxsIzdcL7ATAyFv3x 0ThDsIrwI0W+g9YJmV4xKgu9MPa8vzI2iAoIy2hLFUw/5/37cHVxhhD3kTUqawrj6Q wwyAsVCpTmoJ9QtzmkM10AFrFs51GIzg9o31q3Q+DmsyaCz0svtxwf7mLnX/h3zgLT zVGXqXqjVcOJQ== From: Mark Brown Date: Tue, 08 Apr 2025 19:49:48 +0100 Subject: [PATCH RFT v15 8/8] selftests/clone3: Test shadow stack support Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250408-clone3-shadow-stack-v15-8-3fa245c6e3be@kernel.org> References: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> In-Reply-To: <20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-c25d1 X-Developer-Signature: v=1; a=openpgp-sha256; l=10198; i=broonie@kernel.org; h=from:subject:message-id; bh=5k3/QTD0kVCASnddHQWSmUjfH8nC3PpTtHcWbgjlz9A=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn9W/sM4PjUTQAnt8i/vq9L0yADXqmYYbcHvsLAZZ1 XDV5A8mJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ/Vv7AAKCRAk1otyXVSH0E47B/ 0Z5EsHDp3kTIWB3OC/1qe72Yi4uCirq0uF2NCTOBiMB2HmzPC4kHlvv95hKNqZaeQvLq3uaKbA3iNb fgMGiQv4/klsGITQIP8Fmag4le7FaqXt7TOLlaW9P6aG5oclWl7xnnFtfaB/n9tw4eGHi5BOmcSdig fSQvB9i9hpBWv3fokNdtyPIIiNFCyHrFsVpEsW9YGSXVmYm2t1Z8R2WLInigO/os7AlCOrdpwHh3rd 6/4vTTGGbF/Rz2v9HVjrr4dtndwuQIR8Z7cKQ9A392SEe7nqN4PyESEKbZUsFSYtXvEBzqjFAzrAnF +pI3HqedIQwhursqX4pn45IkXIKwJt X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Add basic test coverage for specifying the shadow stack for a newly created thread via clone3(), including coverage of the newly extended argument structure. We check that a user specified shadow stack can be provided, and that invalid combinations of parameters are rejected. In order to facilitate testing on systems without userspace shadow stack support we manually enable shadow stacks on startup, this is architecture specific due to the use of an arch_prctl() on x86. Due to interactions with potential userspace locking of features we actually detect support for shadow stacks on the running system by attempting to allocate a shadow stack page during initialisation using map_shadow_stack(), warning if this succeeds when the enable failed. In order to allow testing of user configured shadow stacks on architectures with that feature we need to ensure that we do not return from the function where the clone3() syscall is called in the child process, doing so would trigger a shadow stack underflow. To do this we use inline assembly rather than the standard syscall wrapper to call clone3(). In order to avoid surprises we also use a syscall rather than the libc exit() function., this should be overly cautious. Acked-by: Shuah Khan Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3.c | 143 +++++++++++++++++++++- tools/testing/selftests/clone3/clone3_selftests.h | 63 ++++++++++ 2 files changed, 205 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c index 5b8b7d640e70..316449c013ca 100644 --- a/tools/testing/selftests/clone3/clone3.c +++ b/tools/testing/selftests/clone3/clone3.c @@ -3,6 +3,7 @@ /* Based on Christian Brauner's clone3() example */ #define _GNU_SOURCE +#include #include #include #include @@ -11,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -19,8 +21,12 @@ #include #include "../kselftest.h" +#include "../ksft_shstk.h" #include "clone3_selftests.h" +static bool shadow_stack_supported; +static size_t max_supported_args_size; + enum test_mode { CLONE3_ARGS_NO_TEST, CLONE3_ARGS_ALL_0, @@ -28,6 +34,10 @@ enum test_mode { CLONE3_ARGS_INVAL_EXIT_SIGNAL_NEG, CLONE3_ARGS_INVAL_EXIT_SIGNAL_CSIG, CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG, + CLONE3_ARGS_SHADOW_STACK, + CLONE3_ARGS_SHADOW_STACK_MISALIGNED, + CLONE3_ARGS_SHADOW_STACK_NO_TOKEN, + CLONE3_ARGS_SHADOW_STACK_NORMAL_MEMORY, }; typedef bool (*filter_function)(void); @@ -44,6 +54,44 @@ struct test { filter_function filter; }; + +/* + * We check for shadow stack support by attempting to use + * map_shadow_stack() since features may have been locked by the + * dynamic linker resulting in spurious errors when we attempt to + * enable on startup. We warn if the enable failed. + */ +static void test_shadow_stack_supported(void) +{ + long ret; + + ret = syscall(__NR_map_shadow_stack, 0, getpagesize(), 0); + if (ret == -1) { + ksft_print_msg("map_shadow_stack() not supported\n"); + } else if ((void *)ret == MAP_FAILED) { + ksft_print_msg("Failed to map shadow stack\n"); + } else { + ksft_print_msg("Shadow stack supportd\n"); + shadow_stack_supported = true; + + if (!shadow_stack_enabled) + ksft_print_msg("Mapped but did not enable shadow stack\n"); + } +} + +static void *get_shadow_stack_page(unsigned long flags) +{ + unsigned long long page; + + page = syscall(__NR_map_shadow_stack, 0, getpagesize(), flags); + if ((void *)page == MAP_FAILED) { + ksft_print_msg("map_shadow_stack() failed: %d\n", errno); + return 0; + } + + return (void *)page; +} + static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) { struct __clone_args args = { @@ -57,6 +105,7 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) } args_ext; pid_t pid = -1; + void *p; int status; memset(&args_ext, 0, sizeof(args_ext)); @@ -89,6 +138,26 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) case CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG: args.exit_signal = 0x00000000000000f0ULL; break; + case CLONE3_ARGS_SHADOW_STACK: + p = get_shadow_stack_page(SHADOW_STACK_SET_TOKEN); + p += getpagesize() - sizeof(void *); + args.shadow_stack_pointer = (unsigned long long)p; + break; + case CLONE3_ARGS_SHADOW_STACK_MISALIGNED: + p = get_shadow_stack_page(SHADOW_STACK_SET_TOKEN); + p += getpagesize() - sizeof(void *) - 1; + args.shadow_stack_pointer = (unsigned long long)p; + break; + case CLONE3_ARGS_SHADOW_STACK_NORMAL_MEMORY: + p = malloc(getpagesize()); + p += getpagesize() - sizeof(void *); + args.shadow_stack_pointer = (unsigned long long)p; + break; + case CLONE3_ARGS_SHADOW_STACK_NO_TOKEN: + p = get_shadow_stack_page(0); + p += getpagesize() - sizeof(void *); + args.shadow_stack_pointer = (unsigned long long)p; + break; } memcpy(&args_ext.args, &args, sizeof(struct __clone_args)); @@ -102,7 +171,12 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) if (pid == 0) { ksft_print_msg("I am the child, my PID is %d\n", getpid()); - _exit(EXIT_SUCCESS); + /* + * Use a raw syscall to ensure we don't get issues + * with manually specified shadow stack and exit handlers. + */ + syscall(__NR_exit, EXIT_SUCCESS); + ksft_print_msg("CHILD FAILED TO EXIT PID is %d\n", getpid()); } ksft_print_msg("I am the parent (%d). My child's pid is %d\n", @@ -184,6 +258,26 @@ static bool no_timenamespace(void) return true; } +static bool have_shadow_stack(void) +{ + if (shadow_stack_supported) { + ksft_print_msg("Shadow stack supported\n"); + return true; + } + + return false; +} + +static bool no_shadow_stack(void) +{ + if (!shadow_stack_supported) { + ksft_print_msg("Shadow stack not supported\n"); + return true; + } + + return false; +} + static size_t page_size_plus_8(void) { return getpagesize() + 8; @@ -327,6 +421,50 @@ static const struct test tests[] = { .expected = -EINVAL, .test_mode = CLONE3_ARGS_NO_TEST, }, + { + .name = "Shadow stack on system with shadow stack", + .size = 0, + .expected = 0, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK, + .filter = no_shadow_stack, + }, + { + .name = "Shadow stack with misaligned address", + .flags = CLONE_VM, + .size = 0, + .expected = -EINVAL, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK_MISALIGNED, + .filter = no_shadow_stack, + }, + { + .name = "Shadow stack with normal memory", + .flags = CLONE_VM, + .size = 0, + .expected = -EFAULT, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK_NORMAL_MEMORY, + .filter = no_shadow_stack, + }, + { + .name = "Shadow stack with no token", + .flags = CLONE_VM, + .size = 0, + .expected = -EINVAL, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK_NO_TOKEN, + .filter = no_shadow_stack, + }, + { + .name = "Shadow stack on system without shadow stack", + .flags = CLONE_VM, + .size = 0, + .expected = -EFAULT, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK_NORMAL_MEMORY, + .filter = have_shadow_stack, + }, }; int main(int argc, char *argv[]) @@ -334,9 +472,12 @@ int main(int argc, char *argv[]) size_t size; int i; + enable_shadow_stack(); + ksft_print_header(); ksft_set_plan(ARRAY_SIZE(tests)); test_clone3_supported(); + test_shadow_stack_supported(); for (i = 0; i < ARRAY_SIZE(tests); i++) test_clone3(&tests[i]); diff --git a/tools/testing/selftests/clone3/clone3_selftests.h b/tools/testing/selftests/clone3/clone3_selftests.h index 939b26c86d42..f1069fab17ba 100644 --- a/tools/testing/selftests/clone3/clone3_selftests.h +++ b/tools/testing/selftests/clone3/clone3_selftests.h @@ -31,12 +31,75 @@ struct __clone_args { __aligned_u64 set_tid; __aligned_u64 set_tid_size; __aligned_u64 cgroup; +#ifndef CLONE_ARGS_SIZE_VER2 +#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */ +#endif + __aligned_u64 shadow_stack_pointer; +#ifndef CLONE_ARGS_SIZE_VER3 +#define CLONE_ARGS_SIZE_VER3 96 /* sizeof fourth published struct */ +#endif }; +/* + * For architectures with shadow stack support we need to be + * absolutely sure that the clone3() syscall will be inline and not a + * function call so we open code. + */ +#ifdef __x86_64__ +static __always_inline pid_t sys_clone3(struct __clone_args *args, size_t size) +{ + register long _num __asm__ ("rax") = __NR_clone3; + register long _args __asm__ ("rdi") = (long)(args); + register long _size __asm__ ("rsi") = (long)(size); + long ret; + + __asm__ volatile ( + "syscall\n" + : "=a"(ret) + : "r"(_args), "r"(_size), + "0"(_num) + : "rcx", "r11", "memory", "cc" + ); + + if (ret < 0) { + errno = -ret; + return -1; + } + + return ret; +} +#elif defined(__aarch64__) +static __always_inline pid_t sys_clone3(struct __clone_args *args, size_t size) +{ + register long _num __asm__ ("x8") = __NR_clone3; + register long _args __asm__ ("x0") = (long)(args); + register long _size __asm__ ("x1") = (long)(size); + register long arg2 __asm__ ("x2") = 0; + register long arg3 __asm__ ("x3") = 0; + register long arg4 __asm__ ("x4") = 0; + + __asm__ volatile ( + "svc #0\n" + : "=r"(_args) + : "r"(_args), "r"(_size), + "r"(_num), "r"(arg2), + "r"(arg3), "r"(arg4) + : "memory", "cc" + ); + + if ((int)_args < 0) { + errno = -((int)_args); + return -1; + } + + return _args; +} +#else static pid_t sys_clone3(struct __clone_args *args, size_t size) { return syscall(__NR_clone3, args, size); } +#endif static inline void test_clone3_supported(void) {