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

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

[Gustavo A. R. Silva]

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@kernel.org>
---
 arch/sparc/include/uapi/asm/openpromio.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/sparc/include/uapi/asm/openpromio.h b/arch/sparc/include/uapi/asm/openpromio.h
index d4494b679e99..2a73ec77aba6 100644
--- a/arch/sparc/include/uapi/asm/openpromio.h
+++ b/arch/sparc/include/uapi/asm/openpromio.h
@@ -10,10 +10,9 @@
  * were chosen to be exactly equal to the SunOS equivalents.
  */
 
-struct openpromio
-{
+struct openpromio {
 	unsigned int oprom_size;	/* Actual size of the oprom_array. */
-	char	oprom_array[1];		/* Holds property names and values. */
+	char	oprom_array[];		/* Holds property names and values. */
 };
 
 #define	OPROMMAXPARAM	4096		/* Maximum size of oprom_array. */
-- 
2.34.1

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

[Kees Cook]

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@kernel.org>

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

-- 
Kees Cook