net: warn, if pf->create does not clear sock->sk on error

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>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20241014153808.51894-9-ignat@cloudflare.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/socket.c b/net/socket.c
index 24b4042990155ae8abc27ec3de7bc520a2fd3b4d..9a8e4452b9b2178317369e4a8a2506ff8cc606ef 100644 (file)
--- 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;
        }