[PATCH] uapi: wireless: Replace zero-length array with flexible-array member

[PATCH] uapi: wireless: Replace zero-length array with flexible-array member

[Gustavo A. R. Silva]

There is a regular need in the kernel to provide a way to declare
having a dynamically sized set of trailing elements in a structure.
Kernel code should always use “flexible array members”[1] for these
cases. The older style of one-element or zero-length arrays should
no longer be used[2].

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/78
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 include/uapi/linux/wireless.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/wireless.h b/include/uapi/linux/wireless.h
index 08967b3f19c8..3c2ad5fae17f 100644
--- a/include/uapi/linux/wireless.h
+++ b/include/uapi/linux/wireless.h
@@ -835,7 +835,7 @@ struct iw_encode_ext {
 			       * individual keys */
 	__u16		alg; /* IW_ENCODE_ALG_* */
 	__u16		key_len;
-	__u8		key[0];
+	__u8		key[];
 };
 
 /* SIOCSIWMLME data */
-- 
2.27.0

Re: [PATCH] uapi: wireless: Replace zero-length array with flexible-array member

[Kees Cook]

On Wed, Feb 16, 2022 at 01:53:06PM -0600, Gustavo A. R. Silva wrote:
> There is a regular need in the kernel to provide a way to declare
> having a dynamically sized set of trailing elements in a structure.
> Kernel code should always use “flexible array members”[1] for these
> cases. The older style of one-element or zero-length arrays should
> no longer be used[2].
> 
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Link: https://github.com/KSPP/linux/issues/78
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

This UAPI change should be fine for any compiler that understood the
older "[0]" syntax.

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

-- 
Kees Cook

Re: [PATCH] uapi: wireless: Replace zero-length array with flexible-array member

[Gustavo A. R. Silva]

On Wed, Feb 16, 2022 at 12:36:27PM -0800, Kees Cook wrote:
> On Wed, Feb 16, 2022 at 01:53:06PM -0600, Gustavo A. R. Silva wrote:
> > There is a regular need in the kernel to provide a way to declare
> > having a dynamically sized set of trailing elements in a structure.
> > Kernel code should always use “flexible array members”[1] for these
> > cases. The older style of one-element or zero-length arrays should
> > no longer be used[2].
> > 
> > [1] https://en.wikipedia.org/wiki/Flexible_array_member
> > [2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays
> > 
> > Link: https://github.com/KSPP/linux/issues/78
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> 
> This UAPI change should be fine for any compiler that understood the
> older "[0]" syntax.
> 
> Reviewed-by: Kees Cook <keescook@chromium.org>

Hi all,

Friendly ping: can someone take this, please?

...I can take this in my -next tree in the meantime.

Thanks
--
Gustavo