[PATCH AUTOSEL 4.19 23/37] rxrpc: rxrpc_peer needs to hold a ref on the rxrpc_local record

Sasha Levin
2019-10-25T13:56:49Z

From: David Howells <dhowells@redhat.com>

[ Upstream commit 9ebeddef58c41bd700419cdcece24cf64ce32276 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/rxrpc/peer_object.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c
index 72b4ad210426e..b91b090217cdb 100644
--- a/net/rxrpc/peer_object.c
+++ b/net/rxrpc/peer_object.c
@@ -220,7 +220,7 @@ 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);
@@ -311,7 +311,6 @@ 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);
@@ -421,6 +420,7 @@ 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);
}

@@ -457,6 +457,7 @@ 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);
}
}
--
2.20.1