Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752991AbdHOMxn (ORCPT ); Tue, 15 Aug 2017 08:53:43 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:51638 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752852AbdHOMxI (ORCPT ); Tue, 15 Aug 2017 08:53:08 -0400 From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Cc: ard.biesheuvel@linaro.org, catalin.marinas@arm.com, james.morse@arm.com, labbott@redhat.com, linux-kernel@vger.kernel.org, luto@amacapital.net, mark.rutland@arm.com, matt@codeblueprint.co.uk, will.deacon@arm.com, kernel-hardening@lists.openwall.com, keescook@chromium.org Subject: [PATCHv2 13/14] arm64: add on_accessible_stack() Date: Tue, 15 Aug 2017 13:50:48 +0100 Message-Id: <1502801449-29246-14-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1502801449-29246-1-git-send-email-mark.rutland@arm.com> References: <1502801449-29246-1-git-send-email-mark.rutland@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2697 Lines: 78 Both unwind_frame() and dump_backtrace() try to check whether a stack address is sane to access, with very similar logic. Both will need updating in order to handle overflow stacks. Factor out this logic into a helper, so that we can avoid further duplication when we add overflow stacks. Signed-off-by: Mark Rutland Cc: Ard Biesheuvel Cc: Catalin Marinas Cc: James Morse Cc: Laura Abbott Cc: Will Deacon --- arch/arm64/include/asm/stacktrace.h | 16 ++++++++++++++++ arch/arm64/kernel/stacktrace.c | 7 +------ arch/arm64/kernel/traps.c | 3 +-- 3 files changed, 18 insertions(+), 8 deletions(-) diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h index 4c68d8a..92ddb6d 100644 --- a/arch/arm64/include/asm/stacktrace.h +++ b/arch/arm64/include/asm/stacktrace.h @@ -57,4 +57,20 @@ static inline bool on_task_stack(struct task_struct *tsk, unsigned long sp) return (low <= sp && sp < high); } +/* + * We can only safely access per-cpu stacks from current in a non-preemptible + * context. + */ +static inline bool on_accessible_stack(struct task_struct *tsk, unsigned long sp) +{ + if (on_task_stack(tsk, sp)) + return true; + if (tsk != current || preemptible()) + return false; + if (on_irq_stack(sp)) + return true; + + return false; +} + #endif /* __ASM_STACKTRACE_H */ diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 35588ca..3144584 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -50,12 +50,7 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) if (!tsk) tsk = current; - /* - * Switching between stacks is valid when tracing current and in - * non-preemptible context. - */ - if (!(tsk == current && !preemptible() && on_irq_stack(fp)) && - !on_task_stack(tsk, fp)) + if (!on_accessible_stack(tsk, fp)) return -EINVAL; frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp)); diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 9633773..d01c598 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -193,8 +193,7 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) if (in_entry_text(frame.pc)) { stack = frame.fp - offsetof(struct pt_regs, stackframe); - if (on_task_stack(tsk, stack) || - (tsk == current && !preemptible() && on_irq_stack(stack))) + if (on_accessible_stack(tsk, stack)) dump_mem("", "Exception stack", stack, stack + sizeof(struct pt_regs)); } -- 1.9.1