From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Morton <akpm@linux-foundation.org>
Date: Wed, 10 Nov 2010 21:08:34 +0000
Subject: Re: [PATCH] lib: vsprintf: fix invalid arg check
Message-Id: <20101110130834.02496b48.akpm@linux-foundation.org>
List-Id: <kernel-janitors.vger.kernel.org>
References: <1289421490-23950-1-git-send-email-segooon@gmail.com>
In-Reply-To: <1289421490-23950-1-git-send-email-segooon@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
To: Vasiliy Kulikov <segooon@gmail.com>
Cc: kernel-janitors@vger.kernel.org, =?ISO-8859-1?Q?Andr=E9?= Goddard Rosa <andre.goddard@gmail.com>, Joe Perches <joe@perches.com>, Frederic Weisbecker <fweisbec@gmail.com>, Bjorn Helgaas <bjorn.helgaas@hp.com>, linux-kernel@vger.kernel.org

On Wed, 10 Nov 2010 23:38:08 +0300
Vasiliy Kulikov <segooon@gmail.com> wrote:

> "size" is size_t.  If we want to check whether it was underflowed
> then we should cast it to ssize_t instead of int.  When
> sizeof(size_t) > sizeof(int) the code sees UINT_MAX as underflow,
> but it is not.
> 

Does this patch fix any actual observed problem?

>  Compile tested.
> 

I guess not.

> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1290,7 +1290,7 @@ int vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
>  
>  	/* Reject out-of-range values early.  Large positive sizes are
>  	   used for unknown buffer sizes. */

Thousands of people would find that comment to be utterly mysterious. 
I am one.

> -	if (WARN_ON_ONCE((int) size < 0))
> +	if (WARN_ON_ONCE((ssize_t) size < 0))
>  		return 0;
>  
>  	str = buf;