From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Rutland Subject: [PATCH 3/3] arm64: kasan: clear stale stack poison Date: Wed, 2 Mar 2016 14:26:18 +0000 Message-ID: <1456928778-22491-4-git-send-email-mark.rutland@arm.com> References: <1456928778-22491-1-git-send-email-mark.rutland@arm.com> Return-path: In-Reply-To: <1456928778-22491-1-git-send-email-mark.rutland@arm.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: akpm@linux-foundation.org, aryabinin@virtuozzo.com, catalin.marinas@arm.com, glider@google.com, lorenzo.pieralisi@arm.com, mark.rutland@arm.com, mingo@redhat.com, peterz@infradead.org, will.deacon@arm.com List-Id: linux-arch.vger.kernel.org Functions which the compiler has instrumented for ASAN place poison on the stack shadow upon entry and remove this poison prior to returning. In the case of cpuidle, CPUs exit the kernel a number of levels deep in C code. Any instrumented functions on this critical path will leave portions of the stack shadow poisoned. If CPUs lose context and return to the kernel via a cold path, we restore a prior context saved in __cpu_suspend_enter are forgotten, and we never remove the poison they placed in the stack shadow area by functions calls between this and the actual exit of the kernel. Thus, (depending on stackframe layout) subsequent calls to instrumented functions may hit this stale poison, resulting in (spurious) KASAN splats to the console. To avoid this, clear any stale poison from the idle thread for a CPU prior to bringing a CPU online. Signed-off-by: Mark Rutland Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Catalin Marinas Cc: Lorenzo Pieralisi Cc: Will Deacon --- arch/arm64/kernel/sleep.S | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S index e33fe33..fd10eb6 100644 --- a/arch/arm64/kernel/sleep.S +++ b/arch/arm64/kernel/sleep.S @@ -145,6 +145,10 @@ ENTRY(cpu_resume_mmu) ENDPROC(cpu_resume_mmu) .popsection cpu_resume_after_mmu: +#ifdef CONFIG_KASAN + mov x0, sp + bl kasan_unpoison_remaining_stack +#endif mov x0, #0 // return zero on success ldp x19, x20, [sp, #16] ldp x21, x22, [sp, #32] -- 1.9.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com ([217.140.101.70]:58801 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751582AbcCBO0q (ORCPT ); Wed, 2 Mar 2016 09:26:46 -0500 From: Mark Rutland Subject: [PATCH 3/3] arm64: kasan: clear stale stack poison Date: Wed, 2 Mar 2016 14:26:18 +0000 Message-ID: <1456928778-22491-4-git-send-email-mark.rutland@arm.com> In-Reply-To: <1456928778-22491-1-git-send-email-mark.rutland@arm.com> References: <1456928778-22491-1-git-send-email-mark.rutland@arm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: akpm@linux-foundation.org, aryabinin@virtuozzo.com, catalin.marinas@arm.com, glider@google.com, lorenzo.pieralisi@arm.com, mark.rutland@arm.com, mingo@redhat.com, peterz@infradead.org, will.deacon@arm.com Message-ID: <20160302142618.56fkGxApu5wOJ9_Ma2AbOlBYX5Q4znVkjUbVfh11upU@z> Functions which the compiler has instrumented for ASAN place poison on the stack shadow upon entry and remove this poison prior to returning. In the case of cpuidle, CPUs exit the kernel a number of levels deep in C code. Any instrumented functions on this critical path will leave portions of the stack shadow poisoned. If CPUs lose context and return to the kernel via a cold path, we restore a prior context saved in __cpu_suspend_enter are forgotten, and we never remove the poison they placed in the stack shadow area by functions calls between this and the actual exit of the kernel. Thus, (depending on stackframe layout) subsequent calls to instrumented functions may hit this stale poison, resulting in (spurious) KASAN splats to the console. To avoid this, clear any stale poison from the idle thread for a CPU prior to bringing a CPU online. Signed-off-by: Mark Rutland Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Catalin Marinas Cc: Lorenzo Pieralisi Cc: Will Deacon --- arch/arm64/kernel/sleep.S | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S index e33fe33..fd10eb6 100644 --- a/arch/arm64/kernel/sleep.S +++ b/arch/arm64/kernel/sleep.S @@ -145,6 +145,10 @@ ENTRY(cpu_resume_mmu) ENDPROC(cpu_resume_mmu) .popsection cpu_resume_after_mmu: +#ifdef CONFIG_KASAN + mov x0, sp + bl kasan_unpoison_remaining_stack +#endif mov x0, #0 // return zero on success ldp x19, x20, [sp, #16] ldp x21, x22, [sp, #32] -- 1.9.1