io_uring/cmd_net: fix too strict requirement on ioctl

Attempting SOCKET_URING_OP_SETSOCKOPT on an AF_NETLINK socket resulted
in an -EOPNOTSUPP, as AF_NETLINK doesn't have an ioctl in its struct
proto, but only in struct proto_ops.

Prior to the blamed commit, io_uring_cmd_sock() only had two cmd_op
operations, both requiring ioctl, thus the check was warranted.

Since then, 4 new cmd_op operations have been added, none of which
depend on ioctl. This patch moves the ioctl check, so it only applies
to the original operations.

AFAICT, the ioctl requirement was unintentional, and it wasn't
visible in the blamed patch within 3 lines of context.

Cc: stable@vger.kernel.org
Fixes: a5d2f99 ("io_uring/cmd: Introduce SOCKET_URING_OP_GETSOCKOPT")
Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Asbjørn Sloth Tønnesen

io_uring/cmd_net.c

@@ -160,16 +160,19 @@ int io_uring_cmd_sock(struct io_uring_cmd *cmd, unsigned int issue_flags)
 	struct proto *prot = READ_ONCE(sk->sk_prot);
 	int ret, arg = 0;
 
-	if (!prot || !prot->ioctl)
-		return -EOPNOTSUPP;
-
 	switch (cmd->cmd_op) {
 	case SOCKET_URING_OP_SIOCINQ:
+		if (!prot || !prot->ioctl)
+			return -EOPNOTSUPP;
+
 		ret = prot->ioctl(sk, SIOCINQ, &arg);
 		if (ret)
 			return ret;
 		return arg;
 	case SOCKET_URING_OP_SIOCOUTQ:
+		if (!prot || !prot->ioctl)
+			return -EOPNOTSUPP;
+
 		ret = prot->ioctl(sk, SIOCOUTQ, &arg);
 		if (ret)
 			return ret;