On Tue, Dec 05, 2017 at 05:11:56PM +0900, Namhyung Kim wrote:
> From c12126c4ff9835f0899619db3ee7b4a3151ff2bb Mon Sep 17 00:00:00 2001
> From: Namhyung Kim <namhy...@kernel.org>
> Date: Tue, 5 Dec 2017 16:54:50 +0900
> Subject: [PATCH] perf/core: Fix overflow on perf_callchain_entry
>
> The commit 97c79a38cd45 add a check whether per-event max stack is
> greater than the global max. But it missed to do it for the first
> event. So if the event had a stack depth greater than the global max,
> it could overflow the callchain entry list.
>
> Reported-by: Fengguang Wu <fengguang...@intel.com>
> Fixes: 97c79a38cd45 ("perf core: Per event callchain limit")
> Signed-off-by: Namhyung Kim <namhy...@kernel.org>
Indeed, nice catch.
Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Ingo, can you make this happen in perf/urgent ?
> ---
> kernel/events/callchain.c | 21 ++++++++++++---------
> 1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
> index 1b2be63c8528..e449e23802eb 100644
> --- a/kernel/events/callchain.c
> +++ b/kernel/events/callchain.c
> @@ -119,19 +119,22 @@ int get_callchain_buffers(int event_max_stack)
> goto exit;
> }
>
> + /*
> + * If requesting per event more than the global cap,
> + * return a different error to help userspace figure this out.
> + *
> + * And also do it here so that we have &callchain_mutex held.
> + */
> + if (event_max_stack > sysctl_perf_event_max_stack) {
> + err = -EOVERFLOW;
> + goto exit;
> + }
> +
> if (count > 1) {
> /* If the allocation failed, give up */
> if (!callchain_cpus_entries)
> err = -ENOMEM;
> - /*
> - * If requesting per event more than the global cap,
> - * return a different error to help userspace figure
> - * this out.
> - *
> - * And also do it here so that we have &callchain_mutex held.
> - */
> - if (event_max_stack > sysctl_perf_event_max_stack)
> - err = -EOVERFLOW;
> +
> goto exit;
> }
>
> --
> 2.15.0
>
