[PATCH][next] nvmem: u-boot-env: replace zero-length array with flexible-array member

[PATCH][next] nvmem: u-boot-env: replace zero-length array with flexible-array member

[Gustavo A. R. Silva]

Zero-length arrays are deprecated[1] and we are moving towards
adopting C99 flexible-array members instead. So, replace zero-length
array declaration in struct u_boot_env_image_broadcom with flex-array
member.

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 [2].

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays [1]
Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [2]
Link: https://github.com/KSPP/linux/issues/78
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 drivers/nvmem/u-boot-env.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvmem/u-boot-env.c b/drivers/nvmem/u-boot-env.c
index 29b1d87a3c51..6b48637d9e64 100644
--- a/drivers/nvmem/u-boot-env.c
+++ b/drivers/nvmem/u-boot-env.c
@@ -45,7 +45,7 @@ struct u_boot_env_image_broadcom {
 	__le32 magic;
 	__le32 len;
 	__le32 crc32;
-	uint8_t data[0];
+	uint8_t data[];
 } __packed;
 
 static int u_boot_env_read(void *context, unsigned int offset, void *val,
-- 
2.34.1

Re: [PATCH][next] nvmem: u-boot-env: replace zero-length array with flexible-array member

[Kees Cook]

On Mon, Jan 09, 2023 at 07:40:10PM -0600, Gustavo A. R. Silva wrote:
> Zero-length arrays are deprecated[1] and we are moving towards
> adopting C99 flexible-array members instead. So, replace zero-length
> array declaration in struct u_boot_env_image_broadcom with flex-array
> member.
> 
> 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 [2].
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays [1]
> Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [2]
> Link: https://github.com/KSPP/linux/issues/78
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

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

-- 
Kees Cook

Re: [PATCH][next] nvmem: u-boot-env: replace zero-length array with flexible-array member

[Rafał Miłecki]

On 2023-01-10 02:40, Gustavo A. R. Silva wrote:
> Zero-length arrays are deprecated[1] and we are moving towards
> adopting C99 flexible-array members instead. So, replace zero-length
> array declaration in struct u_boot_env_image_broadcom with flex-array
> member.
> 
> 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 [2].

I also handled this issue in my
[PATCH V2 4/6] nvmem: u-boot-env: convert to layout driver
https://lore.kernel.org/linux-arm-kernel/20230111073102.8147-4-zajec5@gmail.com/

Re: [PATCH][next] nvmem: u-boot-env: replace zero-length array with flexible-array member

[Kees Cook]

On Fri, Jan 13, 2023 at 07:41:02AM +0100, Rafał Miłecki wrote:
> On 2023-01-10 02:40, Gustavo A. R. Silva wrote:
> > Zero-length arrays are deprecated[1] and we are moving towards
> > adopting C99 flexible-array members instead. So, replace zero-length
> > array declaration in struct u_boot_env_image_broadcom with flex-array
> > member.
> > 
> > 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 [2].
> 
> I also handled this issue in my
> [PATCH V2 4/6] nvmem: u-boot-env: convert to layout driver
> https://lore.kernel.org/linux-arm-kernel/20230111073102.8147-4-zajec5@gmail.com/

Ah-ha, thanks! Looks good. :)

-- 
Kees Cook