From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: [PATCH v2 10/13] x86/dumpstack: Try harder to get a call trace on stack overflow Date: Fri, 17 Jun 2016 13:00:46 -0700 Message-ID: References: Return-path: In-Reply-To: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org 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. Signed-off-by: Andy Lutomirski --- arch/x86/kernel/dumpstack.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index d4d085e27d04..9cdf05d768cf 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -89,7 +89,7 @@ static inline int valid_stack_ptr(struct thread_info *tinfo, else return 0; } - return p > t && p < t + THREAD_SIZE - size; + return p >= t && p < t + THREAD_SIZE - size; } unsigned long @@ -100,6 +100,13 @@ print_context_stack(struct thread_info *tinfo, { 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)tinfo - (unsigned long)stack < PAGE_SIZE) + stack = (unsigned long *)tinfo; + while (valid_stack_ptr(tinfo, stack, sizeof(*stack), end)) { unsigned long addr; -- 2.5.5 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.136]:59482 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933659AbcFQUBO (ORCPT ); Fri, 17 Jun 2016 16:01:14 -0400 From: Andy Lutomirski Subject: [PATCH v2 10/13] x86/dumpstack: Try harder to get a call trace on stack overflow Date: Fri, 17 Jun 2016 13:00:46 -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: <20160617200046.vvjA3AN6k9efPmag46g-bt1f3nd11DpbG5C4hEhFrlI@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. Signed-off-by: Andy Lutomirski --- arch/x86/kernel/dumpstack.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index d4d085e27d04..9cdf05d768cf 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -89,7 +89,7 @@ static inline int valid_stack_ptr(struct thread_info *tinfo, else return 0; } - return p > t && p < t + THREAD_SIZE - size; + return p >= t && p < t + THREAD_SIZE - size; } unsigned long @@ -100,6 +100,13 @@ print_context_stack(struct thread_info *tinfo, { 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)tinfo - (unsigned long)stack < PAGE_SIZE) + stack = (unsigned long *)tinfo; + while (valid_stack_ptr(tinfo, stack, sizeof(*stack), end)) { unsigned long addr; -- 2.5.5