Re: [PATCH 2/5] scsi: BusLogic: Avoid unbounded `vsprintf' use

From: Khalid Aziz <khalid@gonehiking.org>
To: "Maciej W. Rozycki" <macro@orcam.me.uk>,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>,
	linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/5] scsi: BusLogic: Avoid unbounded `vsprintf' use
Date: Fri, 16 Apr 2021 13:54:24 -0600	[thread overview]
Message-ID: <1dd4eb71-05e5-6da4-bfec-01883d1ac7b3@gonehiking.org> (raw)
In-Reply-To: <alpine.DEB.2.21.2104141521190.44318@angie.orcam.me.uk>

On 4/14/21 4:39 PM, Maciej W. Rozycki wrote:
> Existing `blogic_msg' invocations do not appear to overrun its internal 
> buffer of a fixed length of 100, which would cause stack corruption, but 
> it's easy to miss with possible further updates and a fix is cheap in 
> performance terms, so limit the output produced into the buffer by using 
> `vsnprintf' rather than `vsprintf'.
> 
> Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
> ---
>  drivers/scsi/BusLogic.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> linux-buslogic-vsnprintf.diff
> Index: linux-macro-ide/drivers/scsi/BusLogic.c
> ===================================================================
> --- linux-macro-ide.orig/drivers/scsi/BusLogic.c
> +++ linux-macro-ide/drivers/scsi/BusLogic.c
> @@ -3588,7 +3588,7 @@ static void blogic_msg(enum blogic_msgle
>  	int len = 0;
>  
>  	va_start(args, adapter);
> -	len = vsprintf(buf, fmt, args);
> +	len = vsnprintf(buf, sizeof(buf), fmt, args);
>  	va_end(args);
>  	if (msglevel == BLOGIC_ANNOUNCE_LEVEL) {
>  		static int msglines = 0;
> 

As Maciej explained in other email that snprintf() does null-terminate
the string, I think this change is fine.

Acked-by: Khalid Aziz <khalid@gonehiking.org>