From ab285f2b5290d92b7ec1a6f9aad54308dadf6157 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 8 Apr 2010 14:05:50 +0200 Subject: 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 Tested-by: Eric Dumazet Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Paul Mackerras Cc: David Miller Cc: Archs --- arch/x86/kernel/dumpstack.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'arch') diff --git a/arch/x86/kernel/dumpstack.h b/arch/x86/kernel/dumpstack.h index e39e77168a37..e1a93be4fd44 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; -- cgit v1.2.3-59-g8ed1b