linux-kernel - Re: [PATCH][REPOST] Check maxlen on strnlen

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Date:	Wed, 7 Sep 2011 17:06:21 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ryan Mallon <rmallon@...il.com>
Cc:	Mark Salter <msalter@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"trivial@...nel.org" <trivial@...nel.org>
Subject: Re: [PATCH][REPOST] Check maxlen on strnlen_user usage

On Thu, 08 Sep 2011 09:54:18 +1000
Ryan Mallon <rmallon@...il.com> wrote:

> strnlen_user returns the length of the string including the nul 
> terminator. In the case where maxlen is reached strnlen_user returns 
> maxlen + 1. Most callsites already check for this condition. Fix the 
> call to strnlen_user in fs/exec.c to check for the maxlen case.
> 
> diff --git a/fs/exec.c b/fs/exec.c
> index 25dcbe5..e19588c 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -481,7 +481,7 @@ static int copy_strings(int argc, struct 
> user_arg_ptr argv,
>   			goto out;
> 
>   		len = strnlen_user(str, MAX_ARG_STRLEN);
> -		if (!len)
> +		if (!len || len>  MAX_ARG_STRLEN)
>   			goto out;
> 
>   		ret = -E2BIG;

The following call to vald_arg_len() already does this?

This change will cause copy_strings() to incorrectly return -EFAULT,
rather than -E2BIG.

Your email client is wordwrapping and space-stuffing the patches, btw.
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