rxrpc: rxrpc_peer needs to hold a ref on the rxrpc_local record

The rxrpc_peer record needs to hold a reference on the rxrpc_local record
it points as the peer is used as a base to access information in the
rxrpc_local record.

This can cause problems in __rxrpc_put_peer(), where we need the network
namespace pointer, and in rxrpc_send_keepalive(), where we need to access
the UDP socket, leading to symptoms like:

    BUG: KASAN: use-after-free in __rxrpc_put_peer net/rxrpc/peer_object.c:411
    [inline]
    BUG: KASAN: use-after-free in rxrpc_put_peer+0x685/0x6a0
    net/rxrpc/peer_object.c:435
    Read of size 8 at addr ffff888097ec0058 by task syz-executor823/24216

Fix this by taking a ref on the local record for the peer record.

Fixes: ace45bec6d77 ("rxrpc: Fix firewall route keepalive")
Fixes: 2baec2c3f854 ("rxrpc: Support network namespacing")
Reported-by: syzbot+b9be979c55f2bea8ed30@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>

diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c
index b700b7e..64830d8 100644 (file)
--- a/net/rxrpc/peer_object.c
+++ b/net/rxrpc/peer_object.c
@@ -216,7 +216,7 @@ struct rxrpc_peer *rxrpc_alloc_peer(struct rxrpc_local *local, gfp_t gfp)
        peer = kzalloc(sizeof(struct rxrpc_peer), gfp);
        if (peer) {
                atomic_set(&peer->usage, 1);
-               peer->local = local;
+               peer->local = rxrpc_get_local(local);
                INIT_HLIST_HEAD(&peer->error_targets);
                peer->service_conns = RB_ROOT;
                seqlock_init(&peer->service_conn_lock);
@@ -307,7 +307,6 @@ void rxrpc_new_incoming_peer(struct rxrpc_sock *rx, struct rxrpc_local *local,
        unsigned long hash_key;
 
        hash_key = rxrpc_peer_hash_key(local, &peer->srx);
-       peer->local = local;
        rxrpc_init_peer(rx, peer, hash_key);
 
        spin_lock(&rxnet->peer_hash_lock);
@@ -417,6 +416,7 @@ static void __rxrpc_put_peer(struct rxrpc_peer *peer)
        list_del_init(&peer->keepalive_link);
        spin_unlock_bh(&rxnet->peer_hash_lock);
 
+       rxrpc_put_local(peer->local);
        kfree_rcu(peer, rcu);
 }
 
@@ -453,6 +453,7 @@ void rxrpc_put_peer_locked(struct rxrpc_peer *peer)
        if (n == 0) {
                hash_del_rcu(&peer->hash_link);
                list_del_init(&peer->keepalive_link);
+               rxrpc_put_local(peer->local);
                kfree_rcu(peer, rcu);
        }
 }