On Sat, Jun 01, 2013 at 08:21:20PM +0200, Oleg Nesterov wrote:
> trinity fuzzer triggered WARN_ONCE("Can't find any breakpoint slot")
> in arch_install_hw_breakpoint() but the problem is not arch-specific.
>
> The problem is, task_bp_pinned(cpu) checks "cpu == iter->cpu" but
> this doesn't account the "all cpus" events with iter->cpu < 0.
>
> This means that, say, register_user_hw_breakpoint(tsk) can happily
> create the arbitrary number > HBP_NUM of breakpoints which can not
> be activated. toggle_bp_task_slot() is equally wrong by the same
> reason and nr_task_bp_pinned[] can have negative entries.
>
> Simple test:
>
> # perl -e 'sleep 1 while 1' &
> # perf record -e mem:0x10,mem:0x10,mem:0x10,mem:0x10,mem:0x10 -p `pidof perl`
>
> Before this patch this triggers the same problem/WARN_ON(), after
> the patch it correctly fails with -ENOSPC.
>
> Reported-by: Vince Weaver <vincent.weaver@xxxxxxxxx>
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
Looks good, thanks!
Acked-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> ---
> kernel/events/hw_breakpoint.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
> index ed1c897..29d3abe 100644
> --- a/kernel/events/hw_breakpoint.c
> +++ b/kernel/events/hw_breakpoint.c
> @@ -120,7 +120,7 @@ static int task_bp_pinned(int cpu, struct perf_event *bp, enum bp_type_idx type)
> list_for_each_entry(iter, &bp_task_head, hw.bp_list) {
> if (iter->hw.bp_target == tsk &&
> find_slot_idx(iter) == type &&
> - cpu == iter->cpu)
> + (iter->cpu < 0 || cpu == iter->cpu))
> count += hw_breakpoint_weight(iter);
> }
>
> --
> 1.5.5.1
>
>
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