Messages in this thread | | | Subject | Re: [PATCH] Fix infinite loop in ARM user perf_event backtrace code | From | Will Deacon <> | Date | Mon, 18 Apr 2011 18:42:24 +0100 |
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Hi Sonny,
On Sat, 2011-04-16 at 04:27 +0100, Sonny Rao wrote: > 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> > --- > arch/arm/kernel/perf_event.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c > index 69cfee0..1e61d60 100644 > --- a/arch/arm/kernel/perf_event.c > +++ b/arch/arm/kernel/perf_event.c > @@ -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); > }
Ok. Please can you put this into Russell's patch system?
Will
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