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[209.132.180.67]) by mx.google.com with ESMTP id q24si4808598ejr.128.2019.10.27.14.34.39; Sun, 27 Oct 2019 14:34:39 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of stable-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=wmaSuoRx; spf=pass (google.com: best guess record for domain of stable-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=stable-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728820AbfJ0Veh (ORCPT + 14 others); Sun, 27 Oct 2019 17:34:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:57016 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728768AbfJ0VKf (ORCPT ); Sun, 27 Oct 2019 17:10:35 -0400 Received: from localhost (100.50.158.77.rev.sfr.net [77.158.50.100]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B6015208C0; Sun, 27 Oct 2019 21:10:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572210634; bh=6u/I12k282DOBG2MRmZ69eO1I+TUxQ9KbrQ2nM3A04A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wmaSuoRxphQ/N1E5qgVtCIjfEGP62HbCXBwk75POoLT3nzBBSNcCdL2B/teMJcRv+ PY8iN2dO7ZO6qkpf44dJEZgqHYVwlRQZ6uhjCTMF2o3OxBDVT1dAsqNxauG9VCrXBW n6mDQMdV4tGkuTFVkKSvsNbSjs5SbzGsW/YH9JhI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , Marc Zyngier , Will Deacon , Ard Biesheuvel Subject: [PATCH 4.14 082/119] arm64: Force SSBS on context switch Date: Sun, 27 Oct 2019 22:00:59 +0100 Message-Id: <20191027203345.704836456@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191027203259.948006506@linuxfoundation.org> References: <20191027203259.948006506@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Marc Zyngier [ Upstream commit cbdf8a189a66001c36007bf0f5c975d0376c5c3a ] On a CPU that doesn't support SSBS, PSTATE[12] is RES0. In a system where only some of the CPUs implement SSBS, we end-up losing track of the SSBS bit across task migration. To address this issue, let's force the SSBS bit on context switch. Fixes: 8f04e8e6e29c ("arm64: ssbd: Add support for PSTATE.SSBS rather than trapping to EL3") Signed-off-by: Marc Zyngier [will: inverted logic and added comments] Signed-off-by: Will Deacon Signed-off-by: Ard Biesheuvel Signed-off-by: Greg Kroah-Hartman --- arch/arm64/include/asm/processor.h | 14 ++++++++++++-- arch/arm64/kernel/process.c | 29 ++++++++++++++++++++++++++++- 2 files changed, 40 insertions(+), 3 deletions(-) --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -148,6 +148,16 @@ static inline void start_thread_common(s regs->pc = pc; } +static inline void set_ssbs_bit(struct pt_regs *regs) +{ + regs->pstate |= PSR_SSBS_BIT; +} + +static inline void set_compat_ssbs_bit(struct pt_regs *regs) +{ + regs->pstate |= PSR_AA32_SSBS_BIT; +} + static inline void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) { @@ -155,7 +165,7 @@ static inline void start_thread(struct p regs->pstate = PSR_MODE_EL0t; if (arm64_get_ssbd_state() != ARM64_SSBD_FORCE_ENABLE) - regs->pstate |= PSR_SSBS_BIT; + set_ssbs_bit(regs); regs->sp = sp; } @@ -174,7 +184,7 @@ static inline void compat_start_thread(s #endif if (arm64_get_ssbd_state() != ARM64_SSBD_FORCE_ENABLE) - regs->pstate |= PSR_AA32_SSBS_BIT; + set_compat_ssbs_bit(regs); regs->compat_sp = sp; } --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -298,7 +298,7 @@ int copy_thread(unsigned long clone_flag childregs->pstate |= PSR_UAO_BIT; if (arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE) - childregs->pstate |= PSR_SSBS_BIT; + set_ssbs_bit(childregs); p->thread.cpu_context.x19 = stack_start; p->thread.cpu_context.x20 = stk_sz; @@ -340,6 +340,32 @@ void uao_thread_switch(struct task_struc } /* + * Force SSBS state on context-switch, since it may be lost after migrating + * from a CPU which treats the bit as RES0 in a heterogeneous system. + */ +static void ssbs_thread_switch(struct task_struct *next) +{ + struct pt_regs *regs = task_pt_regs(next); + + /* + * Nothing to do for kernel threads, but 'regs' may be junk + * (e.g. idle task) so check the flags and bail early. + */ + if (unlikely(next->flags & PF_KTHREAD)) + return; + + /* If the mitigation is enabled, then we leave SSBS clear. */ + if ((arm64_get_ssbd_state() == ARM64_SSBD_FORCE_ENABLE) || + test_tsk_thread_flag(next, TIF_SSBD)) + return; + + if (compat_user_mode(regs)) + set_compat_ssbs_bit(regs); + else if (user_mode(regs)) + set_ssbs_bit(regs); +} + +/* * We store our current task in sp_el0, which is clobbered by userspace. Keep a * shadow copy so that we can restore this upon entry from userspace. * @@ -367,6 +393,7 @@ __notrace_funcgraph struct task_struct * contextidr_thread_switch(next); entry_task_switch(next); uao_thread_switch(next); + ssbs_thread_switch(next); /* * Complete any pending TLB or cache maintenance on this CPU in case