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

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Date:   Thu, 22 Jun 2023 17:14:51 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] sparc: openpromio: Address -Warray-bounds warning

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>
---
 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