linux-kernel - Re: [patch] perf tool buffer overflow in perf_header__read_build

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Date:   Fri, 26 Jul 2019 16:05:41 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Vince Weaver <vincent.weaver@...ne.edu>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: [patch] perf tool buffer overflow in perf_header__read_build_ids

Em Tue, Jul 23, 2019 at 04:42:30PM -0400, Vince Weaver escreveu:
> Hello
> 
> my perf_tool_fuzzer has found another issue, this one a buffer overflow
> in perf_header__read_build_ids.  The build id filename is read in with a 
> filename length read from the perf.data file, but this can be longer than
> PATH_MAX which will smash the stack.
> 
> This might not be the right fix, not sure if filename should be NUL
> terminated or not.
> 
> Signed-off-by: Vince Weaver <vincent.weaver@...ne.edu>
> 
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index c24db7f4909c..9a893a26e678 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -2001,6 +2001,9 @@ static int perf_header__read_build_ids(struct perf_header *header,
>  			perf_event_header__bswap(&bev.header);
>  
>  		len = bev.header.size - sizeof(bev);
> +
> +		if (len>PATH_MAX) len=PATH_MAX;
> +

Humm, I wonder if we shouldn't just declare the whole file invalid like
you did with the previous patch?

- Arnaldo

>  		if (readn(input, filename, len) != len)
>  			goto out;
>  		/*