linux-kernel - Re: BUG: KASAN: slab-out-of-bounds in perf_callchain

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Message-ID: <20171206163951.fyden6m4vamkjbqi@hirez.programming.kicks-ass.net>
Date:   Wed, 6 Dec 2017 17:39:51 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Fengguang Wu <fengguang.wu@...el.com>,
        linux-kernel@...r.kernel.org, Wang Nan <wangnan0@...wei.com>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Will Deacon <will.deacon@....com>, lkp@...org,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        kernel-team@....com
Subject: Re: BUG: KASAN: slab-out-of-bounds in perf_callchain_user+0x494/0x530

On Thu, Dec 07, 2017 at 12:49:57AM +0900, Namhyung Kim wrote:

> So, are you ok with this?

yeah, that should work.

> diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
> index 1b2be63c8528..ee0ba22d3993 100644
> --- a/kernel/events/callchain.c
> +++ b/kernel/events/callchain.c
> @@ -137,8 +137,11 @@ int get_callchain_buffers(int event_max_stack)
>  
>         err = alloc_callchain_buffers();
>  exit:
> -       if (err)
> -               atomic_dec(&nr_callchain_events);
> +       if (err) {
> +               /* might race with put_callchain_buffers() */
> +               if (atomic_dec_and_test(&nr_callchain_events))
> +                       release_callchain_buffers();
> +       }
>  
>         mutex_unlock(&callchain_mutex);
>