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authorDavid Howells <dhowells@redhat.com>2018-09-27 17:13:09 +0300
committerDavid Howells <dhowells@redhat.com>2018-09-28 12:32:49 +0300
commit0099dc589bfa7caf6f2608c4cbc1181cfee22b0c (patch)
treefd071d7aab3762ba2ab377892cb4c250923d50b8 /net/rxrpc/peer_object.c
parent403fc2a138457f1071b186786a7589ef7382c8bc (diff)
downloadlinux-0099dc589bfa7caf6f2608c4cbc1181cfee22b0c.tar.xz
rxrpc: Make service call handling more robust
Make the following changes to improve the robustness of the code that sets up a new service call: (1) Cache the rxrpc_sock struct obtained in rxrpc_data_ready() to do a service ID check and pass that along to rxrpc_new_incoming_call(). This means that I can remove the check from rxrpc_new_incoming_call() without the need to worry about the socket attached to the local endpoint getting replaced - which would invalidate the check. (2) Cache the rxrpc_peer struct, thereby allowing the peer search to be done once. The peer is passed to rxrpc_new_incoming_call(), thereby saving the need to repeat the search. This also reduces the possibility of rxrpc_publish_service_conn() BUG()'ing due to the detection of a duplicate connection, despite the initial search done by rxrpc_find_connection_rcu() having turned up nothing. This BUG() shouldn't ever get hit since rxrpc_data_ready() *should* be non-reentrant and the result of the initial search should still hold true, but it has proven possible to hit. I *think* this may be due to __rxrpc_lookup_peer_rcu() cutting short the iteration over the hash table if it finds a matching peer with a zero usage count, but I don't know for sure since it's only ever been hit once that I know of. Another possibility is that a bug in rxrpc_data_ready() that checked the wrong byte in the header for the RXRPC_CLIENT_INITIATED flag might've let through a packet that caused a spurious and invalid call to be set up. That is addressed in another patch. (3) Fix __rxrpc_lookup_peer_rcu() to skip peer records that have a zero usage count rather than stopping and returning not found, just in case there's another peer record behind it in the bucket. (4) Don't search the peer records in rxrpc_alloc_incoming_call(), but rather either use the peer cached in (2) or, if one wasn't found, preemptively install a new one. Fixes: 8496af50eb38 ("rxrpc: Use RCU to access a peer's service connection tree") Signed-off-by: David Howells <dhowells@redhat.com>
Diffstat (limited to 'net/rxrpc/peer_object.c')
-rw-r--r--net/rxrpc/peer_object.c35
1 files changed, 11 insertions, 24 deletions
diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c
index 1dc7648e3eff..70083e8fb6e5 100644
--- a/net/rxrpc/peer_object.c
+++ b/net/rxrpc/peer_object.c
@@ -124,11 +124,9 @@ static struct rxrpc_peer *__rxrpc_lookup_peer_rcu(
struct rxrpc_net *rxnet = local->rxnet;
hash_for_each_possible_rcu(rxnet->peer_hash, peer, hash_link, hash_key) {
- if (rxrpc_peer_cmp_key(peer, local, srx, hash_key) == 0) {
- if (atomic_read(&peer->usage) == 0)
- return NULL;
+ if (rxrpc_peer_cmp_key(peer, local, srx, hash_key) == 0 &&
+ atomic_read(&peer->usage) > 0)
return peer;
- }
}
return NULL;
@@ -299,34 +297,23 @@ static struct rxrpc_peer *rxrpc_create_peer(struct rxrpc_local *local,
}
/*
- * Set up a new incoming peer. The address is prestored in the preallocated
- * peer.
+ * Set up a new incoming peer. There shouldn't be any other matching peers
+ * since we've already done a search in the list from the non-reentrant context
+ * (the data_ready handler) that is the only place we can add new peers.
*/
-struct rxrpc_peer *rxrpc_lookup_incoming_peer(struct rxrpc_local *local,
- struct rxrpc_peer *prealloc)
+void rxrpc_new_incoming_peer(struct rxrpc_local *local, struct rxrpc_peer *peer)
{
- struct rxrpc_peer *peer;
struct rxrpc_net *rxnet = local->rxnet;
unsigned long hash_key;
- hash_key = rxrpc_peer_hash_key(local, &prealloc->srx);
- prealloc->local = local;
- rxrpc_init_peer(prealloc, hash_key);
+ hash_key = rxrpc_peer_hash_key(local, &peer->srx);
+ peer->local = local;
+ rxrpc_init_peer(peer, hash_key);
spin_lock(&rxnet->peer_hash_lock);
-
- /* Need to check that we aren't racing with someone else */
- peer = __rxrpc_lookup_peer_rcu(local, &prealloc->srx, hash_key);
- if (peer && !rxrpc_get_peer_maybe(peer))
- peer = NULL;
- if (!peer) {
- peer = prealloc;
- hash_add_rcu(rxnet->peer_hash, &peer->hash_link, hash_key);
- list_add_tail(&peer->keepalive_link, &rxnet->peer_keepalive_new);
- }
-
+ hash_add_rcu(rxnet->peer_hash, &peer->hash_link, hash_key);
+ list_add_tail(&peer->keepalive_link, &rxnet->peer_keepalive_new);
spin_unlock(&rxnet->peer_hash_lock);
- return peer;
}
/*