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

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Message-ID: <d563cca7-57c6-289a-f551-a378f219aed4@gmail.com>
Date:   Sat, 18 Mar 2023 14:00:55 +0100
From:   Bodo Stroesser <bostroesser@...il.com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     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 17.03.23 17:59, 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>
> ---
>   include/uapi/linux/target_core_user.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/target_core_user.h b/include/uapi/linux/target_core_user.h
> index fbd8ca67e107..f925a77f19ed 100644
> --- a/include/uapi/linux/target_core_user.h
> +++ b/include/uapi/linux/target_core_user.h
> @@ -119,7 +119,7 @@ struct tcmu_cmd_entry {
>   			__u64 cdb_off;
>   			__u64 __pad1;
>   			__u64 __pad2;
> -			struct iovec iov[0];
> +			__DECLARE_FLEX_ARRAY(struct iovec, iov);
>   		} req;
>   		struct {
>   			__u8 scsi_status;

Looks good. Thank you.

Reviewed-by: Bodo Stroesser <bostroesser@...il.com>