Re: [PATCH 1/1] s390/dasd: fix string length handling

From: Nick Desaulniers <ndesaulniers@google.com>
To: Heiko Carstens <hca@linux.ibm.com>
Cc: "Jens Axboe" <axboe@kernel.dk>,
	"Stefan Haberland" <sth@linux.ibm.com>,
	"Jan Höppner" <hoeppner@linux.ibm.com>,
	"Peter Oberparleiter" <oberpar@linux.ibm.com>,
	linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-block@vger.kernel.org, nathan@kernel.org,
	llvm@lists.linux.dev, "David Laight" <David.Laight@aculab.com>
Subject: Re: [PATCH 1/1] s390/dasd: fix string length handling
Date: Mon, 28 Aug 2023 15:46:52 -0700	[thread overview]
Message-ID: <ZO0j3M8KFWeEznXy@google.com> (raw)
In-Reply-To: <20230828153142.2843753-2-hca@linux.ibm.com>

On Mon, Aug 28, 2023 at 05:31:42PM +0200, Heiko Carstens wrote:
> Building dasd_eckd.o with latest clang reveals this bug:
> 
>     CC      drivers/s390/block/dasd_eckd.o
>       drivers/s390/block/dasd_eckd.c:1082:3: warning: 'snprintf' will always be truncated;
>       specified size is 1, but format string expands to at least 11 [-Wfortify-source]
>        1082 |                 snprintf(print_uid, sizeof(*print_uid),
>             |                 ^
>       drivers/s390/block/dasd_eckd.c:1087:3: warning: 'snprintf' will always be truncated;
>       specified size is 1, but format string expands to at least 10 [-Wfortify-source]
>        1087 |                 snprintf(print_uid, sizeof(*print_uid),
>             |                 ^
> 
> Fix this by moving and using the existing UID_STRLEN for the arrays
> that are being written to. Also rename UID_STRLEN to DASD_UID_STRLEN
> to clarify its scope.
> 
> Fixes: 23596961b437 ("s390/dasd: split up dasd_eckd_read_conf")
> Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Thanks for the patch! Nathan just reported a bunch of these. I took a
look at these two and thought "yeah that's clearly a bug in the kernel
sources." Fix LGTM.

Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://github.com/ClangBuiltLinux/linux/issues/1923
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

I also like David's idea of passing `char ident [DASD_UID_STRLEN]`, too,
but I don't feel strongly either way.