net/packet: fix memory leak in packet_set_ring()

syzbot found we can leak memory in packet_set_ring(), if user application
provides buggy parameters.

Fixes: 7f953ab ("af_packet: TX_RING support for TPACKET_V3")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/packet/af_packet.c

@@ -4314,7 +4314,7 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
 				    req3->tp_sizeof_priv ||
 				    req3->tp_feature_req_word) {
 					err = -EINVAL;
-					goto out;
+					goto out_free_pg_vec;
 				}
 			}
 			break;
@@ -4378,6 +4378,7 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
 			prb_shutdown_retire_blk_timer(po, rb_queue);
 	}
 
+out_free_pg_vec:
 	if (pg_vec)
 		free_pg_vec(pg_vec, order, req->tp_block_nr);
 out: