Re: [PATCH] crypto: nx - Fix packed layout in struct nx842_crypto_header

[Thorsten Blum <thorsten.blum@linux.dev>]

On Tue, Mar 17, 2026 at 05:40:02PM -0600, Gustavo A. R. Silva wrote:
> struct nx842_crypto_header is declared with the __packed attribute,
> however	the fields grouped with struct_group_tagged() were not packed.
> This caused the grouped header portion of the structure to lose the
> packed layout guarantees of the containing structure.
> 
> Fix this by replacing struct_group_tagged() with __struct_group(...,
> ..., __packed, ...) so the grouped fields are packed, and the original
> layout is preserved, restoring the intended packed layout of the
> structure.
> 
> Before changes:
> struct nx842_crypto_header {
> 	union {
> 		struct {
> 			__be16     magic;                /*     0     2 */
> 			__be16     ignore;               /*     2     2 */
> 			u8         groups;               /*     4     1 */
> 		};                                       /*     0     6 */
> 		struct nx842_crypto_header_hdr hdr;      /*     0     6 */
> 	};                                               /*     0     6 */
> 	struct nx842_crypto_header_group group[];        /*     6     0 */
> 
> 	/* size: 6, cachelines: 1, members: 2 */
> 	/* last cacheline: 6 bytes */
> } __attribute__((__packed__));
> 
> After changes:
> struct nx842_crypto_header {
> 	union {
> 		struct {
> 			__be16     magic;                /*     0     2 */
> 			__be16     ignore;               /*     2     2 */
> 			u8         groups;               /*     4     1 */
> 		} __attribute__((__packed__));           /*     0     5 */
> 		struct nx842_crypto_header_hdr hdr;      /*     0     5 */
> 	};                                               /*     0     5 */
> 	struct nx842_crypto_header_group group[];        /*     5     0 */
> 
> 	/* size: 5, cachelines: 1, members: 2 */
> 	/* last cacheline: 5 bytes */
> } __attribute__((__packed__));
> 
> Fixes: 1e6b251ce175 ("crypto: nx - Avoid -Wflex-array-member-not-at-end warning")
> Cc: stable@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
>  drivers/crypto/nx/nx-842.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Thorsten Blum <thorsten.blum@linux.dev>