Subject: [PATCH net-next v2 2/2] KEYS: annotate struct user_key_payload with __counted_by

From: Thorsten Blum <[email-masked]>
Date: Fri, 10 Apr 2026 00:57:05 +0200

Add the __counted_by() compiler attribute to the flexible array member
'data' to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.

Signed-off-by: Thorsten Blum <[email-masked]>
---
Changes in v2:
- Use __aligned(8) as suggested by David
- v1: https://lore.kernel.org/lkml/[email-masked]/

Cc: [email-masked]
---
 include/keys/user-type.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/keys/user-type.h b/include/keys/user-type.h
index 386c31432789..c29ed9f5d300 100644
--- a/include/keys/user-type.h
+++ b/include/keys/user-type.h
@@ -27,7 +27,8 @@
 struct user_key_payload {
 	struct rcu_head	rcu;		/* RCU destructor */
 	unsigned short	datalen;	/* length of this data */
-	char		data[] __aligned(__alignof__(u64)); /* actual data */
+	char		data[]		/* actual data */
+			__aligned(8) __counted_by(datalen);
 };
 
 extern struct key_type key_type_user;