[GIT PULL] perf fix
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From: Frederic Weisbecker on 8 Apr 2010 13:40 Ingo, Please pull the perf/urgent branch that can be found at: git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing.git perf/urgent Thanks, Frederic --- Frederic Weisbecker (1): perf: Fix unsafe frame rewinding with hot regs fetching arch/x86/kernel/dumpstack.h | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-) --- commit ab285f2b5290d92b7ec1a6f9aad54308dadf6157 Author: Frederic Weisbecker <fweisbec(a)gmail.com> Date: Thu Apr 8 14:05:50 2010 +0200 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(a)gmail.com> Signed-off-by: Frederic Weisbecker <fweisbec(a)gmail.com> Tested-by: Eric Dumazet <eric.dumazet(a)gmail.com> Cc: Peter Zijlstra <a.p.zijlstra(a)chello.nl> Cc: Arnaldo Carvalho de Melo <acme(a)redhat.com> Cc: Paul Mackerras <paulus(a)samba.org> Cc: David Miller <davem(a)davemloft.net> Cc: Archs <linux-arch(a)vger.kernel.org> 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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |