[lxc-devel] [PATCH 1/6] fix integer overflow in setproctitle

Serge Hallyn serge.hallyn at ubuntu.com
Mon Apr 13 19:05:24 UTC 2015


Quoting Tycho Andersen (tycho.andersen at canonical.com):
> 1. prctl() only accepts longs, so we can just scan the stat file as longs.

?  That's not what the  manpage tells me.

> 2. check overflow before addition
> 
> Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> ---
>  src/lxc/utils.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/src/lxc/utils.c b/src/lxc/utils.c
> index 1df6e8f..cc12ecd 100644
> --- a/src/lxc/utils.c
> +++ b/src/lxc/utils.c
> @@ -1599,7 +1599,7 @@ int setproctitle(char *title)
>  	char buf[2048], *tmp;
>  	FILE *f;
>  	int i, len, ret = 0;
> -	unsigned long arg_start, arg_end, env_start, env_end;
> +	long arg_start, arg_end, env_start, env_end;
>  
>  	f = fopen_cloexec("/proc/self/stat", "r");
>  	if (!f) {
> @@ -1624,7 +1624,7 @@ int setproctitle(char *title)
>  	if (!tmp)
>  		return -1;
>  
> -	i = sscanf(tmp, "%lu %lu %lu %lu", &arg_start, &arg_end, &env_start, &env_end);
> +	i = sscanf(tmp, "%ld %ld %ld %ld", &arg_start, &arg_end, &env_start, &env_end);
>  	if (i != 4) {
>  		return -1;
>  	}
> @@ -1644,15 +1644,21 @@ int setproctitle(char *title)
>  		if (len >= arg_end - arg_start) {
>  			env_start = env_end;
>  		}
> +
> +		/* check overflow */
> +		if (arg_start + len < 0) {
> +			return -1;
> +		}
> +
>  		arg_end = arg_start + len;
>  	}
>  
>  	strcpy((char*)arg_start, title);
>  
> -	ret |= prctl(PR_SET_MM, PR_SET_MM_ARG_START,   (long)arg_start, 0, 0);
> -	ret |= prctl(PR_SET_MM, PR_SET_MM_ARG_END,     (long)arg_end, 0, 0);
> -	ret |= prctl(PR_SET_MM, PR_SET_MM_ENV_START,   (long)env_start, 0, 0);
> -	ret |= prctl(PR_SET_MM, PR_SET_MM_ENV_END,     (long)env_end, 0, 0);
> +	ret |= prctl(PR_SET_MM, PR_SET_MM_ARG_START,   arg_start, 0, 0);
> +	ret |= prctl(PR_SET_MM, PR_SET_MM_ARG_END,     arg_end, 0, 0);
> +	ret |= prctl(PR_SET_MM, PR_SET_MM_ENV_START,   env_start, 0, 0);
> +	ret |= prctl(PR_SET_MM, PR_SET_MM_ENV_END,     env_end, 0, 0);
>  
>  	return ret;
>  }
> -- 
> 2.1.4
> 
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