linux-kernel - Re: [PATCH 09/15] perf tools: validate perf event header size

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Message-ID: <20130625131826.GD23329@krava.brq.redhat.com>
Date:	Tue, 25 Jun 2013 15:18:26 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 09/15] perf tools: validate perf event header size

On Mon, Jun 24, 2013 at 04:16:06PM +0300, Adrian Hunter wrote:
> 'size' includes the header so must be at least
> 'sizeof(struct perf_event_header)'.  Error out
> immediately if that is not the case.  Also
> don't byte-swap the header until it is actually
> "fetched" from the mmap region.
> 
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>  tools/perf/util/session.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 19ea888..7e0d605 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -1094,8 +1094,10 @@ more:
>  		perf_event_header__bswap(&event->header);
>  
>  	size = event->header.size;
> -	if (size == 0)
> -		size = 8;
> +	if (size < sizeof(struct perf_event_header)) {
> +		pr_err("bad event header size\n");
> +		goto out_err;
> +	}
>  
>  	if (size > cur_size) {
>  		void *new = realloc(buf, size);
> @@ -1161,12 +1163,12 @@ fetch_mmaped_event(struct perf_session *session,
>  
>  	event = (union perf_event *)(buf + head);
>  
> -	if (session->header.needs_swap)
> -		perf_event_header__bswap(&event->header);
> -
>  	if (head + event->header.size > mmap_size)
>  		return NULL;

dont we need to swap first before using event->header.size?

jirka
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