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

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Message-ID: <ZO0j3M8KFWeEznXy@google.com>
Date:   Mon, 28 Aug 2023 15:46:52 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Heiko Carstens <hca@...ux.ibm.com>
Cc:     Jens Axboe <axboe@...nel.dk>, Stefan Haberland <sth@...ux.ibm.com>,
        Jan Höppner <hoeppner@...ux.ibm.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, nathan@...nel.org,
        llvm@...ts.linux.dev, David Laight <David.Laight@...lab.com>
Subject: Re: [PATCH 1/1] s390/dasd: fix string length handling

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@...ux.ibm.com>
> Signed-off-by: Heiko Carstens <hca@...ux.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@...nel.org>
Closes: https://github.com/ClangBuiltLinux/linux/issues/1923
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

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