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Subject: Re: [PATCH] perf: fix raw sample size if no sampling data is
 attached
From: Peter Zijlstra <peterz@infradead.org>
To: Robert Richter <robert.richter@amd.com>
Cc: Stephane Eranian <eranian@google.com>, Ingo Molnar <mingo@elte.hu>,
       LKML <linux-kernel@vger.kernel.org>
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Date: Fri, 07 May 2010 17:41:54 +0200
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On Fri, 2010-05-07 at 17:28 +0200, Robert Richter wrote:
> From 6373951f1c660400650066b73c3bb2f6d232be67 Mon Sep 17 00:00:00 2001
> From: Robert Richter <robert.richter@amd.com>
> Date: Fri, 7 May 2010 15:49:56 +0200
> Subject: [PATCH] perf: fix raw sample size if no sampling data is
> attached
> 
> The header size of a raw sample is not included in the total size of a
> raw data sample. Thus, if no data is attached the size must be
> null. In this case a buffer overflow may occur when copying the
> sampling data.
> 
But there is data, a whole u32 of value 0. Your patch breaks things.

> Signed-off-by: Robert Richter <robert.richter@amd.com>
> ---
>  kernel/perf_event.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/perf_event.c b/kernel/perf_event.c
> index 9dbe8cd..f6ddae9 100644
> --- a/kernel/perf_event.c
> +++ b/kernel/perf_event.c
> @@ -3229,7 +3229,7 @@ void perf_output_sample(struct
> perf_output_handle *handle,
>                                 u32     size;
>                                 u32     data;
>                         } raw = {
> -                               .size = sizeof(u32),
> +                               .size = 0,
>                                 .data = 0,
>                         };
>                         perf_output_put(handle, raw);