linux-kernel - Re: [PATCH 20/73] perf machine: Null-terminate version char array upon fgets(/proc/version) error

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Message-Id: <2D532F76-A57F-4CC4-BAA5-B466AFC0305D@gmail.com>
Date:   Fri, 17 May 2019 20:05:39 -0400
From:   Donald Yandt <donald.yandt@...il.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Avi Kivity <avi@...lladb.com>, Jiri Olsa <jolsa@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Yanmin Zhang <yanmin_zhang@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 20/73] perf machine: Null-terminate version char array upon fgets(/proc/version) error

Thank you Arnaldo for signing my patch.

     I think we should use version 4 of my patch and return NULL instead of null-terminating for efficiency.

Thanks,

Donald

> On May 17, 2019, at 3:35 PM, Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> 
> From: Donald Yandt <donald.yandt@...il.com>
> 
> If fgets() fails due to any other error besides end-of-file, the version
> char array may not even be null-terminated.
> 
> Signed-off-by: Donald Yandt <donald.yandt@...il.com>
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Avi Kivity <avi@...lladb.com>
> Cc: Jiri Olsa <jolsa@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Yanmin Zhang <yanmin_zhang@...ux.intel.com>
> Fixes: a1645ce12adb ("perf: 'perf kvm' tool for monitoring guest performance from host")
> Link: http://lkml.kernel.org/r/20190514110100.22019-1-donald.yandt@gmail.com
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.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 3c520baa198c..28a9541c4835 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
>