From mboxrd@z Thu Jan 1 00:00:00 1970 From: Frederic Weisbecker Subject: [PATCH] perf: Fix unsafe frame rewinding with hot regs fetching Date: Thu, 8 Apr 2010 14:32:11 +0200 Message-ID: <20100408123209.GA6096@nowhere> References: <1269568362-13690-1-git-send-regression-fweisbec@gmail.com> <1269568362-13690-6-git-send-regression-fweisbec@gmail.com> <1270720640.2215.43.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-pz0-f193.google.com ([209.85.222.193]:60786 "EHLO mail-pz0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753940Ab0DHMcT (ORCPT ); Thu, 8 Apr 2010 08:32:19 -0400 Content-Disposition: inline In-Reply-To: <1270720640.2215.43.camel@edumazet-laptop> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Eric Dumazet Cc: Ingo Molnar , LKML , Peter Zijlstra , Arnaldo Carvalho de Melo , Paul Mackerras , David Miller , Archs On Thu, Apr 08, 2010 at 11:57:20AM +0200, Eric Dumazet wrote: > Hello > > Current linux-2.6 tree panics on my dev machine > > 64 bit kernel, 32bit user land > CONFIG_FRAME_POINTER=y > > perf timechart record & > > Instant crash > > Call Trace: > perf_trace_sched_switch+0xd5/0x120 > schedule+0x6b5/0x860 > retint_careful+0xd/0x21 > > RIP ffffffff81010955 perf_arch_fetch_caller_regs+0x15/0x40 > CR2: 00000000d21f1422 > > > rewind_frame_pointer() is probably wrong. > > No test performed to check frame is in current stack, or > that (!user_mode_vm(regs)) > > > static inline unsigned long rewind_frame_pointer(int n) > { > struct stack_frame *frame; > > get_bp(frame); > > #ifdef CONFIG_FRAME_POINTER > while (n--) > frame = frame->next_frame; > #endif > > return (unsigned long)frame; > } > > > Can you please test this fix? Thanks. --- >From 60d5c4e8498efc4a01abceef54ad3bc91993bf41 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 8 Apr 2010 14:05:50 +0200 Subject: [PATCH] perf: Fix unsafe frame rewinding with hot regs fetching When we fetch the hot regs and rewind to the nth caller, it might happen that we dereference a frame pointer outside the kernel stack boundaries, like in this example: perf_trace_sched_switch+0xd5/0x120 schedule+0x6b5/0x860 retint_careful+0xd/0x21 Since we directly dereference a userspace frame pointer here while rewinding behind retint_careful, this may end up in a crash. Fix this by simply using probe_kernel_address() when we rewind the frame pointer. This issue will have a much more proper fix in the next version of the perf_arch_fetch_caller_regs() API that will only need to rewind to the first caller. Reported-by: Eric Dumazet Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Paul Mackerras Cc: David Miller Cc: Archs --- arch/x86/kernel/dumpstack.h | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/dumpstack.h b/arch/x86/kernel/dumpstack.h index e39e771..e1a93be 100644 --- a/arch/x86/kernel/dumpstack.h +++ b/arch/x86/kernel/dumpstack.h @@ -14,6 +14,8 @@ #define get_bp(bp) asm("movq %%rbp, %0" : "=r" (bp) :) #endif +#include + extern void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs, unsigned long *stack, unsigned long bp, char *log_lvl); @@ -42,8 +44,10 @@ static inline unsigned long rewind_frame_pointer(int n) get_bp(frame); #ifdef CONFIG_FRAME_POINTER - while (n--) - frame = frame->next_frame; + while (n--) { + if (probe_kernel_address(&frame->next_frame, frame)) + break; + } #endif return (unsigned long)frame; -- 1.6.2.3