linux-kernel - Re: [PATCH 09/10] scsi: aic94xx: Remove snprintf() from sysfs call-backs and replace with sysfs

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Message-ID: <202402092307.FC979BCBA5@keescook>
Date: Fri, 9 Feb 2024 23:13:10 -0800
From: Kees Cook <keescook@...omium.org>
To: Lee Jones <lee@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
	"James E.J. Bottomley" <jejb@...ux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	John Garry <john.g.garry@...cle.com>,
	Luben Tuikov <luben_tuikov@...ptec.com>, linux-scsi@...r.kernel.org
Subject: Re: [PATCH 09/10] scsi: aic94xx: Remove snprintf() from sysfs
 call-backs and replace with sysfs_emit()

On Thu, Feb 08, 2024 at 08:44:21AM +0000, Lee Jones wrote:
> Since snprintf() has the documented, but still rather strange trait of
> returning the length of the data that *would have been* written to the
> array if space were available, rather than the arguably more useful
> length of data *actually* written, it is usually considered wise to use
> something else instead in order to avoid confusion.
> 
> In the case of sysfs call-backs, new wrappers exist that do just that.

Actually, a treewide replacement for snprintf(dst, PAGE_SIZE, ... to
sysfs_emit might be workable too. Here's the .cocci file I made quickly:

@replace@
expression DST;
@@

- snprintf(DST, PAGE_SIZE,
+ sysfs_emit(DST,
  ...)

This produced almost 1000 changes:
 118 files changed, 964 insertions(+), 958 deletions(-)

Some need some manual examination, like:

arch/powerpc/platforms/ps3/system-bus.c:modalias_show() does:

        return (len >= PAGE_SIZE) ? (PAGE_SIZE - 1) : len;

which isn't needed any more.

Regardless,

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

-Kees

-- 
Kees Cook