From patchwork Tue Apr 15 23:31:09 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 881498 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 194CC21B9FF; Tue, 15 Apr 2025 23:31:56 +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=1744759917; cv=none; b=PK52krbCv2iRg7DvRPCEsUjF2gpXDsTjBxaY2nhOKSWQUo0SX3sk+gT7PGG+3usv87Y69Bz/lsIO4Iqbe9FIF+jKpGSKD5/fip5mGj0FRgJJAQZ8p2AfIsdDbCnJuwn7W8H3OZWbAkrX8SRCCWgWG4/fzBSl5YWVA0F6WdWlyvI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744759917; c=relaxed/simple; bh=k56u8xsssiS9PLGw09HLQ5Vh+FXmTGCSWgKOA+mivOY=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=M8+C8T/4rQVWcxy11Ihrds79oblQ2bks28akxhn9c3hKs0dBr73pETnbL9tM8tcwigOa2qHJV8Ptpi3qpyLKzaTafSoVWxpBcjuHqjr+0WQVxXQ9T85JyEHZ3eIKtReYehSJRAkA4ROhgVdkMXYDUFn2wO8bMYGGLeUg9Sc93kM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ig+t/Osg; 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="Ig+t/Osg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0184C4CEE9; Tue, 15 Apr 2025 23:31:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744759916; bh=k56u8xsssiS9PLGw09HLQ5Vh+FXmTGCSWgKOA+mivOY=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Ig+t/OsgFE/xxTxmZIeRoAYwDwvJ//IKrcyfQ43Cx+FdT2QaBzoCaQjkJtRSN+YCc l8zJAIG4c3FMviEzAX0p0rgB+jCyrBUCybYfT0El3Bw6f4ZeSeKkrSBEnQRA2jXtR1 5jyiAJ7YThtld133nHPDYfEoPwjIktYOB4ENpSmJq4SZYU8MaDkEHK4RtM7TOr9sMy xdWeCAdr/tB67bKDXoXvkutO11k68IH/b5YP7r5b2RJt3Dvn4iJSvHwVM6bL+h08mt /eK+iLXikKZaJCio9+jMsON+C76FkkEEESPk7PByk+vDNl/w3KhhZ7xDn3O9lIOwh2 T+8jgj8fEiZoQ== From: Mark Brown Date: Wed, 16 Apr 2025 00:31:09 +0100 Subject: [PATCH RFT v16 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: <20250416-clone3-shadow-stack-v16-2-2ffc9ca3917b@kernel.org> References: <20250416-clone3-shadow-stack-v16-0-2ffc9ca3917b@kernel.org> In-Reply-To: <20250416-clone3-shadow-stack-v16-0-2ffc9ca3917b@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/pANAwAKASTWi3JdVIfQAcsmYgBn/uxVXO4DncWW2JRSLnW0e97xpa40aI8JELgLmONV Vk3IyTqJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ/7sVQAKCRAk1otyXVSH0IPjB/ 4zS7GY3SkA6nhXU5/WED3xQ17CooiFvObNkC5r5iwnmUmxpHNbczZ1+peZZHUVJls3/AsXfi3s+Al6 yvnvRxB0lEWfQIk5kCTiDqt2khbowx2JIDK1NUNzxIMJxB5Jat2E6xw1VdqaXbAxwbHjsMNynZwsUi uSlKxN6nqjyux/o/5e1RPhyqU9fbKB4qPTE4PmFatBP7f8paksg/gy0nHHpmJ3u0FXvszqZ16PxJ9R OfrzDQRmefBZQoenPiQLdilW5WBbskdKnwbkspel1ao0Hjw+EUJxSXOU6RrfKZXC3rYDKiepZ4px3z A/ginkehjflO2pQnFFIFmPoQ6C+Z3M 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 15 23:31:11 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 881497 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 8B77B2957C5; Tue, 15 Apr 2025 23:32:08 +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=1744759928; cv=none; b=HcogJmzhQ2kSzrP+cmyQKjT+w0PDJasKIoxJgaZli4W+102DyxA30kV7xB+Ct9BE3vhImAl6OITRLd8Ufk/6+9BJ2QyTBNUKCSHhkvVAg8BQaFgTkdeBf6aEj30MzVryjjWRYIsVQBtrXmi6eQNb2jFpKwEXwkgSDu2dyX3igMQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744759928; c=relaxed/simple; bh=W9YJQtN3Bo1hY1TQG+0VI73bjJTxf9tjNhYIGVb9qT4=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=R6DMZqkyBVEhRHxTxTEkX/8lCKs9h4lkfDIsduaWmwD2olxqrU4mZV7DEji+r2ohMVxZdtXKxbmc8tJcNWzFk/nprcXKiLZDbQF4qBfXTnoNtLt+w/xJz7f8m7vKfFj4zWanjyTYWECKTnRJf/9xbYGX2upgUqQjWndb/4HHMow= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rw/ZODP+; 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="rw/ZODP+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED98DC4CEEB; Tue, 15 Apr 2025 23:32:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744759928; bh=W9YJQtN3Bo1hY1TQG+0VI73bjJTxf9tjNhYIGVb9qT4=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=rw/ZODP+xzYJUOSSO375wxvhxAc+zrmuwxFFIlz91WrQlvcNMWNvQca+J2lngFyCU +GU4fCi0/+TMZhkhFUbck+VLHLiJ/EclnTRL4ROUbSyvuvLHHQmphOz+v8f+lNdgrR t24mE6WrV5Yt9oSzj62EVHdvaE9yerioOkiSDLeK8hIH4L7YcMOydweOiUt/jY+hAq 16YaPhb82Tb/MF/aIodY/JqI/B7qyfwlbcKs0F0095BY31bH6aGI8r7qVmL+zOwprj 1TP0uLgQfn3q3tC9dIZrVKizqVTv6J+h/OsQNam8NKjYSqT3EyQG6JgpXg5IxVTKNE 6j7mQeYEl56OQ== From: Mark Brown Date: Wed, 16 Apr 2025 00:31:11 +0100 Subject: [PATCH RFT v16 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: <20250416-clone3-shadow-stack-v16-4-2ffc9ca3917b@kernel.org> References: <20250416-clone3-shadow-stack-v16-0-2ffc9ca3917b@kernel.org> In-Reply-To: <20250416-clone3-shadow-stack-v16-0-2ffc9ca3917b@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=16254; i=broonie@kernel.org; h=from:subject:message-id; bh=W9YJQtN3Bo1hY1TQG+0VI73bjJTxf9tjNhYIGVb9qT4=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn/uxWZQq4DXGHLTmLtoFbL/sgRUAmHrBcrID/NRGm rezPFg2JATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ/7sVgAKCRAk1otyXVSH0Fa0B/ 4uTZCWVW5rStG7kAKevmmKx6PSMK5TXCkg43bRLQ7N20p+9oju2/+Ytyh8dZxGSU3SzyXssdkQmF31 8c5HtXsGFzmEQD+EwA6lUPPK1vxhz1PvGwGgQC77ISapJE2yeXTjcjq42gEdv3V3enis8AYFgnqeIm 39J9yNGqOAx22djk9uVxZivV19yQM1fig+pePDTrt5TbYsY8Lxa/h06VrdsrUyQ604ZT2+XyjH8WMt edePbw5iT+ylTTrr0FsWVXI8O+8xECWTzOTqZ6Cs4VCBv3pQAQAGgV0E/LpPiMcwEVdJ296FCIvIjS RVMFlXzyBSnwYLVshhCTHXjbUojxKU 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 | 53 +++++++++++++++++++++- 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 | 9 ++-- kernel/fork.c | 96 +++++++++++++++++++++++++++++++++++----- 8 files changed, 230 insertions(+), 26 deletions(-) diff --git a/arch/arm64/mm/gcs.c b/arch/arm64/mm/gcs.c index 1f633a482558..586494f7669b 100644 --- a/arch/arm64/mm/gcs.c +++ b/arch/arm64/mm/gcs.c @@ -43,8 +43,23 @@ 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_token) + 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_token) { + tsk->thread.gcs_base = 0; + tsk->thread.gcs_size = 0; return 0; + } if (!task_gcs_el0_enabled(tsk)) return 0; @@ -68,6 +83,42 @@ 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_token; + 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..8cce74ee0d96 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 = page_address(page); + int offset, token; + unsigned long ssp; + u64 expected; + + if (!features_enabled(ARCH_SHSTK_SHSTK)) + return 0; + + token = args->shadow_stack_token; + ssp = token + 8; + expected = (ssp + FRAME_SIZE) | BIT(0); + offset = offset_in_page(token); + + if (!cmpxchg_to_user_page(vma, page, token, (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_token) + 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_token) { + shstk->base = 0; + shstk->size = 0; + return args->shadow_stack_token + 8; + } /* * 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..c34f3cb68822 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_token; }; /* @@ -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..9cf5c419e109 100644 --- a/include/uapi/linux/sched.h +++ b/include/uapi/linux/sched.h @@ -84,6 +84,7 @@ * 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_token: Pointer to shadow stack token at top of stack. * * The structure is versioned by size and thus extensible. * New struct members must go at the end of the struct and @@ -101,12 +102,14 @@ struct clone_args { __aligned_u64 set_tid; __aligned_u64 set_tid_size; __aligned_u64 cgroup; + __aligned_u64 shadow_stack_token; }; #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..98f19bd1f35d 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_token) + return 0; + + mm = get_task_mm(p); + if (!mm) + return -EFAULT; + + mmap_read_lock(mm); + + addr = untagged_addr_remote(mm, args->shadow_stack_token); + 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_token) != + 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_token = args.shadow_stack_token, }; 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_token) + return true; + + if (!IS_ALIGNED(kargs->shadow_stack_token, 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 15 23:31:13 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 881496 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 1B50719C54E; Tue, 15 Apr 2025 23:32:20 +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=1744759941; cv=none; b=dEOF/X6GUv+T2o//yq7TF4HNbFAZe/trXfH9yKTgodwJ8o79zO0vDOawWY0SyDT8bxjJlV0RkMUL9yx2spKcblv8UWcDtQ9/jlCgXCjR4+KIenaxN7a/Wtvq+LjYvPk1WdHB4lTtCN1zNNDR7kbkQEGLSVdxWC2wU5Y95Ev4iig= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744759941; 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=lqIHoTFEMyje1RTtR58jJSctdKbxnRUASh9+YaTJWD2yEqnSoyI4ULtXAlv1ju+6GArmqmzDIBT5fwv2FZ3Kiv+buiwOr3yFtmcxiLnoWTtTcJ62gh3MEl8WDJqtcgnJBJVW0wT4ejQt7OeU1hfKK+UlfnZWRibJnb1MQULhbtI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SE6iovMf; 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="SE6iovMf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E7F01C4CEE7; Tue, 15 Apr 2025 23:32:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744759940; bh=1QQTqlYHUjewASmFh86Dd+jl+m64vZGkDAeB+lVVa3I=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=SE6iovMftMuEL9lXVuQTnLTZmFNRzWc/QfKstO014/PgTrPmLEDG0qjHjSwKijqwV OsNu7UnGUo4+PG1tkIpcHLAkD80I0Uum6NeKfvWZZNIt0ymgG1uT2KLnEdzcIn5OZn xH3Y+YjFsNg15O/BkyliHkdQJDs/NzyKqo5eeNJuOoGe7VJ9nMMoFBG/flJkFQi/BN k2bR4SW1/B1xavq4IJXbvXTen/PaThTF5pSHRPiKQgbSopJqK6q0hL/URparIpNeDg SK+9y1CQJGv69x5kYQfajqDNtqUdxfzvfb1TxGbLov72OoQQLp9XDNTkyfwRdEa7I5 Rlu1lIvQwwYSA== From: Mark Brown Date: Wed, 16 Apr 2025 00:31:13 +0100 Subject: [PATCH RFT v16 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: <20250416-clone3-shadow-stack-v16-6-2ffc9ca3917b@kernel.org> References: <20250416-clone3-shadow-stack-v16-0-2ffc9ca3917b@kernel.org> In-Reply-To: <20250416-clone3-shadow-stack-v16-0-2ffc9ca3917b@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/pANAwAKASTWi3JdVIfQAcsmYgBn/uxYoIznsmrDeaKI7cAfJZ+UsQoZHFWKd9D4or/0 BURIRiWJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ/7sWAAKCRAk1otyXVSH0BPfB/ 9J6ojLziWb3d80AGaYNahTBf1hervoWnlbdyHe1nlajj8tfxRLBzfj9jmauqxt0hFCShGyDv5SkCR9 ZfIFBDf2yfG1QkIe80pOZyHA9TyyJDjEVoETG6mXWj1tmHENIleNjrd3q4dUpU2JK9Yhphw3of7VrP lhRM7HEVI52nfnTCzay4ETManqDPHrArKcCYLnLP3UgJwDkO3LKiE7C00kEXYJIOSz6idkpe5Q9toD TAt9zZEMAPuqW0BapqX/c9WF1KqxrDJdV7c+5x/sV4uCf2c83KtN6QvChQsWNv7vJr6huLjdEUs4Lg TXLOVIi30zs+CBxgO0kKLFh78vbvNO 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 15 23:31:15 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 881495 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 AE0AD2D8DD0; Tue, 15 Apr 2025 23:32:32 +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=1744759952; cv=none; b=HEFrsUhucwpiMMxsVHziVi7ORNweQ1HfL1hH4/mc9xbrVGBJHxLBhx2RU0Tj3a5ofpnhnVkNd5iIQLkAwdhJoKjxtsTRAyLzWjQtn2a0ek9SanAW2ysXkdB2AqDMwSCd2qNKYcSSYLUEg8AVckIfEWK5ol8IIw4z/BHh/flBALs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744759952; c=relaxed/simple; bh=qiy3S/IosP5v7tFLu6mQoJBkT+oZKHlJCEp70J0xwdQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=J24hfw7Z4REAv7l5H+/82TCZMHvl0b6AzjECZpEGmcD4NbKLYbAoA9DvVJXhMUDp4GdcuJcT3aLAvytzk3/JrTeGDWC2BZbzf4XuzUm61QThnn/+dPF7WmhV3g/KTqr+lzQzTJoniMn18vuI5NwFYlQ3XdSosCwpY5EwhlEUvoI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aWdoXbYS; 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="aWdoXbYS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 003CEC4CEE7; Tue, 15 Apr 2025 23:32:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744759952; bh=qiy3S/IosP5v7tFLu6mQoJBkT+oZKHlJCEp70J0xwdQ=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=aWdoXbYSsSwybKUSQCoOMuBZ6BWJzOommA3PSwT3cZ9wzyKcAfA0ngHw+Ttaeaxv6 vukIKaBXY3c6bHihvvRij2D1hLcuthp68qJ9HOAa7r1hJhqsTTRqCowEw9uSuElLnt euI8OgxJCE1gyHVF6Er/UKwXt3FcEpQDSx4q/JSzXLAwZBxKxo3p4c/bQomxjusT35 TIA2B2ahuMeNnE1SuQBTWv6pfCH7Bow9ipUtvN64pAvrhK5lYufKnpjfPjNtZYHhuc h2RMdiTJel1gvFqXlXunN+P/R/GZMU4i82OGc8PkHHEQ44YMcfmC0AvSuvMS6EgpnA 9B4dP+6ekL8rQ== From: Mark Brown Date: Wed, 16 Apr 2025 00:31:15 +0100 Subject: [PATCH RFT v16 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: <20250416-clone3-shadow-stack-v16-8-2ffc9ca3917b@kernel.org> References: <20250416-clone3-shadow-stack-v16-0-2ffc9ca3917b@kernel.org> In-Reply-To: <20250416-clone3-shadow-stack-v16-0-2ffc9ca3917b@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=10188; i=broonie@kernel.org; h=from:subject:message-id; bh=qiy3S/IosP5v7tFLu6mQoJBkT+oZKHlJCEp70J0xwdQ=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn/uxafybAzWSQeyIw/BDexQ3kBwCfPxJ44RmbBhbA J07BpU2JATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ/7sWgAKCRAk1otyXVSH0JR0B/ 4+fNjlYNoMYRtcMdGfXx1r8VjOFNvIUgKqiK0cspFL2RMJXDJNi0xzEussL6BxTx58/LFKL6EVconY ANcI01V5cUiIIpEkGu7yXAhtWMirLlKhk9iga904PHEsC9Vg8Qy7Ac/XPRwwe05Iy53uh+/ZZfKVTM yYtNf3VqGyrpyPQpWDx7OL3wok1hZ2lbGkCRe2uWiGUIOqIz48qC4Q0PEIDIz0ETmOLVLyEn1EsLN2 sInYOaQYib6LzlInNP7+YpA7B1/VQw5VwvIKTzWio8r0sEzCiXN6Sc6iixGo5OtOMhL+jjgQHor1JR JKtu147oCJXCe7O1/Q+C3q8mSb8cw5 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..6fd2b3238e2c 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_token = (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_token = (unsigned long long)p; + break; + case CLONE3_ARGS_SHADOW_STACK_NORMAL_MEMORY: + p = malloc(getpagesize()); + p += getpagesize() - sizeof(void *); + args.shadow_stack_token = (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_token = (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..8151c4fc971a 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_token; +#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) {