From ab285f2b5290d92b7ec1a6f9aad54308dadf6157 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <fweisbec@gmail.com>
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 <eric.dumazet@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: David Miller <davem@davemloft.net>
Cc: Archs <linux-arch@vger.kernel.org>
---
arch/x86/kernel/dumpstack.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
(limited to 'arch/x86/kernel/dumpstack.h')
diff --git a/arch/x86/kernel/dumpstack.h b/arch/x86/kernel/dumpstack.h
index e39e77168a3..e1a93be4fd4 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;
--
cgit v1.2.3-70-g09d2