diff options
| author | David Howells <dhowells@redhat.com> | 2019-07-30 14:42:50 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-08-29 08:28:35 +0200 |
| commit | 0d68fbc2d07b5914fb8712b05549bd558fccf1c8 (patch) | |
| tree | b9be8b2104fa0c83803cd7b493ffc88919141d0f /net/rxrpc | |
| parent | 63dd147e7af0e69e5275191ff077e2c7f4ff53f8 (diff) | |
rxrpc: Fix potential deadlock
[ Upstream commit 60034d3d146b11922ab1db613bce062dddc0327a ]
There is a potential deadlock in rxrpc_peer_keepalive_dispatch() whereby
rxrpc_put_peer() is called with the peer_hash_lock held, but if it reduces
the peer's refcount to 0, rxrpc_put_peer() calls __rxrpc_put_peer() - which
the tries to take the already held lock.
Fix this by providing a version of rxrpc_put_peer() that can be called in
situations where the lock is already held.
The bug may produce the following lockdep report:
============================================
WARNING: possible recursive locking detected
5.2.0-next-20190718 #41 Not tainted
--------------------------------------------
kworker/0:3/21678 is trying to acquire lock:
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at: spin_lock_bh
/./include/linux/spinlock.h:343 [inline]
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:
__rxrpc_put_peer /net/rxrpc/peer_object.c:415 [inline]
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:
rxrpc_put_peer+0x2d3/0x6a0 /net/rxrpc/peer_object.c:435
but task is already holding lock:
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at: spin_lock_bh
/./include/linux/spinlock.h:343 [inline]
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:
rxrpc_peer_keepalive_dispatch /net/rxrpc/peer_event.c:378 [inline]
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:
rxrpc_peer_keepalive_worker+0x6b3/0xd02 /net/rxrpc/peer_event.c:430
Fixes: 330bdcfadcee ("rxrpc: Fix the keepalive generator [ver #2]")
Reported-by: syzbot+72af434e4b3417318f84@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'net/rxrpc')
| -rw-r--r-- | net/rxrpc/ar-internal.h | 1 | ||||
| -rw-r--r-- | net/rxrpc/peer_event.c | 2 | ||||
| -rw-r--r-- | net/rxrpc/peer_object.c | 18 |
3 files changed, 20 insertions, 1 deletions
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index 03e0fc8c183f..a4c341828b72 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -1057,6 +1057,7 @@ void rxrpc_destroy_all_peers(struct rxrpc_net *); struct rxrpc_peer *rxrpc_get_peer(struct rxrpc_peer *); struct rxrpc_peer *rxrpc_get_peer_maybe(struct rxrpc_peer *); void rxrpc_put_peer(struct rxrpc_peer *); +void rxrpc_put_peer_locked(struct rxrpc_peer *); /* * proc.c diff --git a/net/rxrpc/peer_event.c b/net/rxrpc/peer_event.c index bd2fa3b7caa7..dc7fdaf20445 100644 --- a/net/rxrpc/peer_event.c +++ b/net/rxrpc/peer_event.c @@ -375,7 +375,7 @@ static void rxrpc_peer_keepalive_dispatch(struct rxrpc_net *rxnet, spin_lock_bh(&rxnet->peer_hash_lock); list_add_tail(&peer->keepalive_link, &rxnet->peer_keepalive[slot & mask]); - rxrpc_put_peer(peer); + rxrpc_put_peer_locked(peer); } spin_unlock_bh(&rxnet->peer_hash_lock); diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c index 5691b7d266ca..71547e8673b9 100644 --- a/net/rxrpc/peer_object.c +++ b/net/rxrpc/peer_object.c @@ -441,6 +441,24 @@ void rxrpc_put_peer(struct rxrpc_peer *peer) } /* + * Drop a ref on a peer record where the caller already holds the + * peer_hash_lock. + */ +void rxrpc_put_peer_locked(struct rxrpc_peer *peer) +{ + const void *here = __builtin_return_address(0); + int n; + + n = atomic_dec_return(&peer->usage); + trace_rxrpc_peer(peer, rxrpc_peer_put, n, here); + if (n == 0) { + hash_del_rcu(&peer->hash_link); + list_del_init(&peer->keepalive_link); + kfree_rcu(peer, rcu); + } +} + +/* * Make sure all peer records have been discarded. */ void rxrpc_destroy_all_peers(struct rxrpc_net *rxnet) |