[PATCH net-next v3 8/9] net: warn, if pf->create does not clear sock->sk on error

[Ignat Korchagin <ignat@cloudflare.com>]

All pf->create implementations have been fixed now to clear sock->sk on
error, when they deallocate the allocated sk object.

Put a warning in place to make sure we don't break this promise in the
future.

Suggested-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
---
 net/socket.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/socket.c b/net/socket.c
index 24b404299015..9a8e4452b9b2 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1576,9 +1576,9 @@ int __sock_create(struct net *net, int family, int type, int protocol,
 	err = pf->create(net, sock, protocol, kern);
 	if (err < 0) {
 		/* ->create should release the allocated sock->sk object on error
-		 * but it may leave the dangling pointer
+		 * and make sure sock->sk is set to NULL to avoid use-after-free
 		 */
-		sock->sk = NULL;
+		DEBUG_NET_WARN_ON_ONCE(sock->sk);
 		goto out_module_put;
 	}
 
-- 
2.39.5