From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755700AbdDRM5K (ORCPT ); Tue, 18 Apr 2017 08:57:10 -0400 Received: from terminus.zytor.com ([65.50.211.136]:55747 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751374AbdDRM5H (ORCPT ); Tue, 18 Apr 2017 08:57:07 -0400 Date: Tue, 18 Apr 2017 05:51:19 -0700 From: tip-bot for Josh Poimboeuf Message-ID: Cc: hpa@zytor.com, jpoimboe@redhat.com, mingo@kernel.org, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, dvlasenk@redhat.com, peterz@infradead.org, tglx@linutronix.de, brgerst@gmail.com, bp@alien8.de, jhladky@redhat.com, luto@kernel.org Reply-To: tglx@linutronix.de, jhladky@redhat.com, luto@kernel.org, brgerst@gmail.com, bp@alien8.de, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, mingo@kernel.org, hpa@zytor.com, jpoimboe@redhat.com, peterz@infradead.org, dvlasenk@redhat.com In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/asm] x86/unwind: Ensure stack pointer is aligned Git-Commit-ID: e335bb51cc15e80ac180701a0d335ef1c050828e X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: e335bb51cc15e80ac180701a0d335ef1c050828e Gitweb: http://git.kernel.org/tip/e335bb51cc15e80ac180701a0d335ef1c050828e Author: Josh Poimboeuf AuthorDate: Mon, 17 Apr 2017 08:44:00 -0500 Committer: Ingo Molnar CommitDate: Tue, 18 Apr 2017 10:30:23 +0200 x86/unwind: Ensure stack pointer is aligned With frame pointers disabled, on some older versions of GCC (like 4.8.3), it's possible for the stack pointer to get aligned at a half-word boundary: 00000000000004d0 : 4d0: 41 57 push %r15 4d2: 41 56 push %r14 4d4: 41 55 push %r13 4d6: 41 54 push %r12 4d8: 55 push %rbp 4d9: 53 push %rbx 4da: 48 83 ec 24 sub $0x24,%rsp In such a case, the unwinder ends up reading the entire stack at the wrong alignment. Then the last read goes past the end of the stack, hitting the stack guard page: BUG: stack guard page was hit at ffffc900217c4000 (stack is ffffc900217c0000..ffffc900217c3fff) kernel stack overflow (page fault): 0000 [#1] SMP ... Fix it by ensuring the stack pointer is properly aligned before unwinding. Reported-by: Jirka Hladky Signed-off-by: Josh Poimboeuf Acked-by: Thomas Gleixner Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Fixes: 7c7900f89770 ("x86/unwind: Add new unwind interface and implementations") Link: http://lkml.kernel.org/r/cff33847cc9b02fa548625aa23268ac574460d8d.1492436590.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/dumpstack.c | 2 +- arch/x86/kernel/unwind_guess.c | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 924f45e..dbce3cc 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -77,7 +77,7 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs, * - softirq stack * - hardirq stack */ - for (regs = NULL; stack; stack = stack_info.next_sp) { + for (regs = NULL; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) { const char *stack_name; /* diff --git a/arch/x86/kernel/unwind_guess.c b/arch/x86/kernel/unwind_guess.c index 22881dd..039f367 100644 --- a/arch/x86/kernel/unwind_guess.c +++ b/arch/x86/kernel/unwind_guess.c @@ -34,7 +34,7 @@ bool unwind_next_frame(struct unwind_state *state) return true; } - state->sp = info->next_sp; + state->sp = PTR_ALIGN(info->next_sp, sizeof(long)); } while (!get_stack_info(state->sp, state->task, info, &state->stack_mask)); @@ -49,7 +49,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, memset(state, 0, sizeof(*state)); state->task = task; - state->sp = first_frame; + state->sp = PTR_ALIGN(first_frame, sizeof(long)); get_stack_info(first_frame, state->task, &state->stack_info, &state->stack_mask);