linux-kernel - Re: [PATCH 03/10] scsi: NCR5380: Replace snprintf() with the safer scnprintf() variant

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Message-ID: <202402092313.D3894DC9@keescook>
Date: Fri, 9 Feb 2024 23:14:01 -0800
From: Kees Cook <keescook@...omium.org>
To: Lee Jones <lee@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
	Finn Thain <fthain@...ux-m68k.org>,
	Michael Schmitz <schmitzmic@...il.com>,
	"James E.J. Bottomley" <jejb@...ux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	drew@...orado.edu, Tnx to <Thomas_Roesch@...maus.de>,
	linux-scsi@...r.kernel.org
Subject: Re: [PATCH 03/10] scsi: NCR5380: Replace snprintf() with the safer
 scnprintf() variant

On Thu, Feb 08, 2024 at 08:44:15AM +0000, Lee Jones wrote:
> There is a general misunderstanding amongst engineers that {v}snprintf()
> returns the length of the data *actually* encoded into the destination
> array.  However, as per the C99 standard {v}snprintf() really returns
> the length of the data that *would have been* written if there were
> enough space for it.  This misunderstanding has led to buffer-overruns
> in the past.  It's generally considered safer to use the {v}scnprintf()
> variants in their place (or even sprintf() in simple cases).  So let's
> do that.
> 
> Link: https://lwn.net/Articles/69419/
> Link: https://github.com/KSPP/linux/issues/105
> Signed-off-by: Lee Jones <lee@...nel.org>

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook