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 <fweisbec@xxxxxxxxx> 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 <eric.dumazet@xxxxxxxxx> Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: David Miller <davem@xxxxxxxxxxxxx> Cc: Archs <linux-arch@xxxxxxxxxxxxxxx> --- 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 <linux/uaccess.h> + 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 -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html