nvme: Annotate struct nvme_dhchap_key with __counted_by

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

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Keith Busch <kbusch@kernel.org>

Author: toblux

include/linux/nvme-auth.h

@@ -11,7 +11,7 @@
 struct nvme_dhchap_key {
 	size_t len;
 	u8 hash;
-	u8 key[];
+	u8 key[] __counted_by(len);
 };
 
 u32 nvme_auth_get_seqnum(void);