linux-kernel - Re: [PATCH][next] sparc: openpromio: Address -Warray-bounds warning

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Message-ID: <202306291257.FF5C86E@keescook>
Date:   Thu, 29 Jun 2023 12:57:54 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] sparc: openpromio: Address -Warray-bounds warning

On Thu, Jun 22, 2023 at 05:14:51PM -0600, Gustavo A. R. Silva wrote:
> One-element arrays are deprecated, and we are replacing them with flexible
> array members instead. So, replace one-element array with flexible-array
> member in struct openpromio.
> 
> Address the following warning found after building (with GCC-13) sparc
> with sparc64_defconfig:
> In function 'opromgetprop',
>     inlined from 'openprom_sunos_ioctl.isra' at drivers/sbus/char/openprom.c:312:11:
> drivers/sbus/char/openprom.c:141:24: warning: array subscript 1 is above array bounds of 'char[1]' [-Warray-bounds=]
>   141 |         op->oprom_array[len] = '\0';
>       |         ~~~~~~~~~~~~~~~^~~~~
> In file included from drivers/sbus/char/openprom.c:31:
> arch/sparc/include/uapi/asm/openpromio.h: In function 'openprom_sunos_ioctl.isra':
> arch/sparc/include/uapi/asm/openpromio.h:16:17: note: while referencing 'oprom_array'
>    16 |         char    oprom_array[1];         /* Holds property names and values. */
>       |                 ^~~~~~~~~~~
> 
> This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
> routines on memcpy() and help us make progress towards globally
> enabling -Warray-bounds.
> 
> This results in no differences in binary output.
> 
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/322
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

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

-- 
Kees Cook