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authorLinus Torvalds <torvalds@woody.osdl.org>2006-11-17 11:14:56 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-11-17 11:14:56 -0800
commit808dbbb6bb61173bf52946a28f99089d2efa4c55 (patch)
tree4d221ed1e66ea09d244b248bb27998ac2efda119 /arch
parent1ff5683043196b9ad628a5de6bf8eeca52ee8bfd (diff)
x86: be more careful when walking back the frame pointer chain
When showing the stack backtrace, make sure that we never accept not only an unchanging frame pointer, but also a frame pointer that moves back down the stack frame. It must always grow up (toward older stack frames). I doubt this has triggered, but a subtly corrupt stack with extremely unlucky contents could cause us to loop forever on a bogus endless frame pointer chain. This review was triggered by much worse problems happening in some of the other stack unwinding code. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/i386/kernel/traps.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 00489b706d2..fe9c5e8e7e6 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -129,15 +129,19 @@ static inline unsigned long print_context_stack(struct thread_info *tinfo,
#ifdef CONFIG_FRAME_POINTER
while (valid_stack_ptr(tinfo, (void *)ebp)) {
+ unsigned long new_ebp;
addr = *(unsigned long *)(ebp + 4);
ops->address(data, addr);
/*
* break out of recursive entries (such as
- * end_of_stack_stop_unwind_function):
+ * end_of_stack_stop_unwind_function). Also,
+ * we can never allow a frame pointer to
+ * move downwards!
*/
- if (ebp == *(unsigned long *)ebp)
+ new_ebp = *(unsigned long *)ebp;
+ if (new_ebp <= ebp)
break;
- ebp = *(unsigned long *)ebp;
+ ebp = new_ebp;
}
#else
while (valid_stack_ptr(tinfo, stack)) {