linux-kernel - Re: [PATCH 1/2] tmon: Check log file for common secuirty issues

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Date:	Tue, 17 Jun 2014 14:13:02 -0700
From:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	linux-kernel@...r.kernel.org, Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH 1/2] tmon: Check log file for common secuirty issues

On Tue, 17 Jun 2014 16:05:08 -0400
Neil Horman <nhorman@...driver.com> wrote:

> The tmon logging system blindly opens its log file on a static path,
> making it very easy for someone to redirect that log information to
> inappropriate places or overwrite other users data.  Do some easy
> checking to make sure we're not logging to a symlink or a file owned
> by another user.
> 
Acked-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>

> Signed-off-by: Neil Horman <nhorman@...driver.com>
> CC: Zhang Rui <rui.zhang@...el.com>
> CC: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
>  tools/thermal/tmon/tmon.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/tools/thermal/tmon/tmon.c b/tools/thermal/tmon/tmon.c
> index b30f531..059e0be 100644
> --- a/tools/thermal/tmon/tmon.c
> +++ b/tools/thermal/tmon/tmon.c
> @@ -142,6 +142,7 @@ static void start_syslog(void)
>  static void prepare_logging(void)
>  {
>  	int i;
> +	struct stat logstat;
>  
>  	if (!logging)
>  		return;
> @@ -152,6 +153,29 @@ static void prepare_logging(void)
>  		return;
>  	}
>  
> +	if (lstat(TMON_LOG_FILE, &logstat) < 0) {
> +		syslog(LOG_ERR, "Unable to stat log file %s\n",
> TMON_LOG_FILE);
> +		fclose(tmon_log);
> +		tmon_log = NULL;
> +		return;
> +	}
> +
> +	/* The log file must be a regular file owned by us */
> +	if (S_ISLNK(logstat.st_mode)) {
> +		syslog(LOG_ERR, "Log file is a symlink.  Will not
> log\n");
> +		fclose(tmon_log);
> +		tmon_log = NULL;
> +		return;
> +	}
> +
> +	if (logstat.st_uid != getuid()) {
> +		syslog(LOG_ERR, "We don't own the log file.  Not
> logging\n");
> +		fclose(tmon_log);
> +		tmon_log = NULL;
> +		return;
> +	}
> +
> +
>  	fprintf(tmon_log, "#----------- THERMAL SYSTEM CONFIG
> -------------\n"); for (i = 0; i < ptdata.nr_tz_sensor; i++) {
>  		char binding_str[33]; /* size of long + 1 */

[Jacob Pan]

-- 
Thanks,

Jacob
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