linux-kernel - Re: [patch] perf tool divide by zero error if f_header.attr

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Date:   Fri, 26 Jul 2019 16:00:16 -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 divide by zero error if f_header.attr_size==0

Em Tue, Jul 23, 2019 at 11:06:01AM -0400, Vince Weaver escreveu:
> Hello
> 
> so I have been having lots of trouble with hand-crafted perf.data files 
> causing segfaults and the like, so I have started fuzzing the perf tool.
> 
> First issue found:
> 
> If f_header.attr_size is 0 in the perf.data file, then perf will crash
> with a divide-by-zero error.
> 
> Signed-off-by: Vince Weaver <vincent.weaver@...ne.edu>


I added this on top:

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 25f89d0790fe..47877f0f6667 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3560,6 +3560,9 @@ int perf_session__read_header(struct perf_session *session)
        }

        if (f_header.attr_size == 0) {
+               pr_err("ERROR: The %s file's attr size field is 0 which is unexpected.\n"
+                      "Was the 'perf record' command properly terminated?\n",
+                      data->file.path);
                return -EINVAL;
        }

[acme@...co perf]$

Thanks, applied.

- Arnaldo

> 
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index c24db7f4909c..26df60ee9460 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -3559,6 +3559,10 @@ int perf_session__read_header(struct perf_session *session)
>  			   data->file.path);
>  	}
>  
> +	if (f_header.attr_size == 0) {
> +		return -EINVAL;
> +	}
> +
>  	nr_attrs = f_header.attrs.size / f_header.attr_size;
>  	lseek(fd, f_header.attrs.offset, SEEK_SET);
>  

-- 

- Arnaldo