linux-kernel - Re: [PATCH v2] tools/perf/util: null-terminate version char array upon error

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Message-ID: <20190514133603.GH3198@kernel.org>
Date:   Tue, 14 May 2019 10:36:03 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Donald Yandt <donald.yandt@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>, linux-kernel@...r.kernel.org,
        Yanmin Zhang <yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH v2] tools/perf/util: null-terminate version char array
 upon error

Em Tue, May 14, 2019 at 07:01:00AM -0400, Donald Yandt escreveu:
> If fgets fails due to any other error besides end-of-file, the version char array may not even be null-terminated.

Thanks, but out of curiosity, was this found just by visual inspection?
Some static analysis tool? An actual problem you stumbled when
processing some /proc/version in a custom kernel?

Also please consider adding a:

Fixes: a1645ce12adb ("perf: 'perf kvm' tool for monitoring guest performance from host")

So that we can get this picked up by the stable kernel trees. I'm adding
it now.

Thanks!

- Arnaldo
 
> Signed-off-by: Donald Yandt <donald.yandt@...il.com>
> ---
>  tools/perf/util/machine.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 3c520baa1..28a9541c4 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1234,8 +1234,9 @@ static char *get_kernel_version(const char *root_dir)
>  	if (!file)
>  		return NULL;
> 
> -	version[0] = '\0';
>  	tmp = fgets(version, sizeof(version), file);
> +	if (!tmp)
> +		*version = '\0';
>  	fclose(file);
> 
>  	name = strstr(version, prefix);
> --
> 2.20.1

-- 

- Arnaldo