Re: [PATCH] audit: Fix check of return value of strnlen_user()

[Paul Moore <paul@paul-moore.com>]

On Tuesday, June 02, 2015 05:08:29 PM Jan Kara wrote:
> strnlen_user() returns 0 when it hits fault, not -1. Fix the test in
> audit_log_single_execve_arg(). Luckily this shouldn't ever happen unless
> there's a kernel bug so it's mostly a cosmetic fix.
> 
> CC: Paul Moore <pmoore@redhat.com>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  kernel/auditsc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 9fb9d1cb83ce..bb947ceeee4d 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -1023,7 +1023,7 @@ static int audit_log_single_execve_arg(struct
> audit_context *context, * for strings that are too long, we should not have
> created
>  	 * any.
>  	 */
> -	if (unlikely((len == -1) || len > MAX_ARG_STRLEN - 1)) {
> +	if (unlikely((len == 0) || len > MAX_ARG_STRLEN - 1)) {

While we're at it, should we make it just "len > MAX_ARG_STRLEN" as well?  
Reading the comments in include/uapi/linux/binfmts.h as well as 
valid_arg_len() that seems to be the correct logic.

>  		WARN_ON(1);
>  		send_sig(SIGKILL, current, 0);
>  		return -1;

-- 
paul moore
www.paul-moore.com