diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index c9cef3782b4a..9d6f1aa65776 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -1116,7 +1116,7 @@ extern void afs_fs_inline_bulk_status(struct afs_operation *);
 
 struct afs_acl {
 	u32	size;
-	u8	data[];
+	u8	data[] __counted_by(size);
 };
 
 extern void afs_fs_fetch_acl(struct afs_operation *);
diff --git a/fs/afs/xattr.c b/fs/afs/xattr.c
index 64b2c0224f62..e19f396aa370 100644
--- a/fs/afs/xattr.c
+++ b/fs/afs/xattr.c
@@ -75,7 +75,7 @@ static bool afs_make_acl(struct afs_operation *op,
 {
 	struct afs_acl *acl;
 
-	acl = kmalloc(sizeof(*acl) + size, GFP_KERNEL);
+	acl = kmalloc(struct_size(acl, data, size), GFP_KERNEL);
 	if (!acl) {
 		afs_op_nomem(op);
 		return false;