linux-hardening - Re: [PATCH][next] uapi: target: Replace fake flex-array with flexible-array member

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Date:   Mon, 20 Mar 2023 11:33:15 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Bodo Stroesser <bostroesser@...il.com>, linux-scsi@...r.kernel.org,
        target-devel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] uapi: target: Replace fake flex-array with
 flexible-array member

On Fri, Mar 17, 2023 at 10:59:48AM -0600, Gustavo A. R. Silva wrote:
> Zero-length arrays as fake flexible arrays are deprecated and we are
> moving towards adopting C99 flexible-array members instead.
> 
> Address the following warning found with GCC-13 and
> -fstrict-flex-arrays=3 enabled:
>   CC      drivers/target/target_core_user.o
> drivers/target/target_core_user.c: In function ‘queue_cmd_ring’:
> drivers/target/target_core_user.c:1096:15: warning: array subscript 0 is outside array bounds of ‘struct iovec[0]’ [-Warray-bounds=]
>  1096 |         iov = &entry->req.iov[0];
>       |               ^~~~~~~~~~~~~~~~~~
> In file included from drivers/target/target_core_user.c:31:
> ./include/uapi/linux/target_core_user.h:122:38: note: while referencing ‘iov’
>   122 |                         struct iovec iov[0];
>       |                                      ^~~
> 
> This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
> routines on memcpy() and help us make progress towards globally
> enabling -fstrict-flex-arrays=3 [1].
> 
> Link: https://github.com/KSPP/linux/issues/21
> Link: https://github.com/KSPP/linux/issues/270
> Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1]
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

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

-- 
Kees Cook