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ARM: 6884/1: Fix infinite loop in ARM user perf_event backtrace code 

The ARM user backtrace code can get into an infinite loop if it
runs into an invalid stack frame which points back to itself.
This situation has been observed in practice.  Fix it by capping
the number of entries in the backtrace.  This is also what other
architectures do in their backtrace code.

Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
Acked-by: Jamie Iles <jamie@jamieiles.com>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Sonny Rao 2011-04-18 22:12:59 +01:00 committed by Russell King
parent 167f829752
commit 860ad7823f
1 changed files with 2 additions and 1 deletions
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3
arch/arm/kernel/perf_event.c
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@ -746,7 +746,8 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
tail = (struct frame_tail __user *)regs->ARM_fp - 1;
while (tail && !((unsigned long)tail & 0x3))
while ((entry->nr < PERF_MAX_STACK_DEPTH) &&
tail && !((unsigned long)tail & 0x3))
tail = user_backtrace(tail, entry);
}