From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: [PATCH v5 11/32] x86/dumpstack: Try harder to get a call trace on stack overflow Date: Mon, 11 Jul 2016 13:53:44 -0700 Message-ID: References: Reply-To: kernel-hardening@lists.openwall.com Return-path: List-Post: List-Help: List-Unsubscribe: List-Subscribe: In-Reply-To: In-Reply-To: References: To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, Borislav Petkov , Nadav Amit , Kees Cook , Brian Gerst , "kernel-hardening@lists.openwall.com" , Linus Torvalds , Josh Poimboeuf , Jann Horn , Heiko Carstens , Andy Lutomirski List-Id: linux-arch.vger.kernel.org If we overflow the stack, print_context_stack will abort. Detect this case and rewind back into the valid part of the stack so that we can trace it. Reviewed-by: Josh Poimboeuf Signed-off-by: Andy Lutomirski --- arch/x86/kernel/dumpstack.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 4eefee06f6fd..de8242d8bb61 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -87,7 +87,7 @@ static inline int valid_stack_ptr(struct task_struct *task, else return 0; } - return p > t && p < t + THREAD_SIZE - size; + return p >= t && p < t + THREAD_SIZE - size; } unsigned long @@ -98,6 +98,14 @@ print_context_stack(struct task_struct *task, { struct stack_frame *frame = (struct stack_frame *)bp; + /* + * If we overflowed the stack into a guard page, jump back to the + * bottom of the usable stack. + */ + if ((unsigned long)task_stack_page(task) - (unsigned long)stack < + PAGE_SIZE) + stack = (unsigned long *)task_stack_page(task); + while (valid_stack_ptr(task, stack, sizeof(*stack), end)) { unsigned long addr; -- 2.7.4 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.136]:34464 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751381AbcGKUy2 (ORCPT ); Mon, 11 Jul 2016 16:54:28 -0400 From: Andy Lutomirski Subject: [PATCH v5 11/32] x86/dumpstack: Try harder to get a call trace on stack overflow Date: Mon, 11 Jul 2016 13:53:44 -0700 Message-ID: In-Reply-To: References: In-Reply-To: References: Sender: linux-arch-owner@vger.kernel.org List-ID: To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, Borislav Petkov , Nadav Amit , Kees Cook , Brian Gerst , "kernel-hardening@lists.openwall.com" , Linus Torvalds , Josh Poimboeuf , Jann Horn , Heiko Carstens , Andy Lutomirski Message-ID: <20160711205344.JjRmEwB2RBCYjRHJvyD3Ude4dradloSt4jMZHs2JNBA@z> If we overflow the stack, print_context_stack will abort. Detect this case and rewind back into the valid part of the stack so that we can trace it. Reviewed-by: Josh Poimboeuf Signed-off-by: Andy Lutomirski --- arch/x86/kernel/dumpstack.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 4eefee06f6fd..de8242d8bb61 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -87,7 +87,7 @@ static inline int valid_stack_ptr(struct task_struct *task, else return 0; } - return p > t && p < t + THREAD_SIZE - size; + return p >= t && p < t + THREAD_SIZE - size; } unsigned long @@ -98,6 +98,14 @@ print_context_stack(struct task_struct *task, { struct stack_frame *frame = (struct stack_frame *)bp; + /* + * If we overflowed the stack into a guard page, jump back to the + * bottom of the usable stack. + */ + if ((unsigned long)task_stack_page(task) - (unsigned long)stack < + PAGE_SIZE) + stack = (unsigned long *)task_stack_page(task); + while (valid_stack_ptr(task, stack, sizeof(*stack), end)) { unsigned long addr; -- 2.7.4