From: David Howells Date: Thu, 27 Sep 2018 14:13:09 +0000 (+0100) Subject: rxrpc: Make service call handling more robust X-Git-Tag: v4.19-rc7~28^2~31^2~2 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=0099dc589bfa7caf6f2608c4cbc1181cfee22b0c;p=linux.git 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 --- diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index e8861cb78070..c72686193d83 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -722,6 +722,8 @@ extern struct workqueue_struct *rxrpc_workqueue; int rxrpc_service_prealloc(struct rxrpc_sock *, gfp_t); void rxrpc_discard_prealloc(struct rxrpc_sock *); struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *, + struct rxrpc_sock *, + struct rxrpc_peer *, struct rxrpc_connection *, struct sk_buff *); void rxrpc_accept_incoming_calls(struct rxrpc_local *); @@ -913,7 +915,8 @@ extern unsigned int rxrpc_closed_conn_expiry; struct rxrpc_connection *rxrpc_alloc_connection(gfp_t); struct rxrpc_connection *rxrpc_find_connection_rcu(struct rxrpc_local *, - struct sk_buff *); + struct sk_buff *, + struct rxrpc_peer **); void __rxrpc_disconnect_call(struct rxrpc_connection *, struct rxrpc_call *); void rxrpc_disconnect_call(struct rxrpc_call *); void rxrpc_kill_connection(struct rxrpc_connection *); @@ -1049,8 +1052,7 @@ struct rxrpc_peer *rxrpc_lookup_peer_rcu(struct rxrpc_local *, struct rxrpc_peer *rxrpc_lookup_peer(struct rxrpc_local *, struct sockaddr_rxrpc *, gfp_t); struct rxrpc_peer *rxrpc_alloc_peer(struct rxrpc_local *, gfp_t); -struct rxrpc_peer *rxrpc_lookup_incoming_peer(struct rxrpc_local *, - struct rxrpc_peer *); +void rxrpc_new_incoming_peer(struct rxrpc_local *, struct rxrpc_peer *); 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 *); diff --git a/net/rxrpc/call_accept.c b/net/rxrpc/call_accept.c index e88f131c1d7f..9c7f26d06a52 100644 --- a/net/rxrpc/call_accept.c +++ b/net/rxrpc/call_accept.c @@ -249,11 +249,11 @@ void rxrpc_discard_prealloc(struct rxrpc_sock *rx) */ static struct rxrpc_call *rxrpc_alloc_incoming_call(struct rxrpc_sock *rx, struct rxrpc_local *local, + struct rxrpc_peer *peer, struct rxrpc_connection *conn, struct sk_buff *skb) { struct rxrpc_backlog *b = rx->backlog; - struct rxrpc_peer *peer, *xpeer; struct rxrpc_call *call; unsigned short call_head, conn_head, peer_head; unsigned short call_tail, conn_tail, peer_tail; @@ -276,21 +276,18 @@ static struct rxrpc_call *rxrpc_alloc_incoming_call(struct rxrpc_sock *rx, return NULL; if (!conn) { - /* No connection. We're going to need a peer to start off - * with. If one doesn't yet exist, use a spare from the - * preallocation set. We dump the address into the spare in - * anticipation - and to save on stack space. - */ - xpeer = b->peer_backlog[peer_tail]; - if (rxrpc_extract_addr_from_skb(local, &xpeer->srx, skb) < 0) - return NULL; - - peer = rxrpc_lookup_incoming_peer(local, xpeer); - if (peer == xpeer) { + if (peer && !rxrpc_get_peer_maybe(peer)) + peer = NULL; + if (!peer) { + peer = b->peer_backlog[peer_tail]; + if (rxrpc_extract_addr_from_skb(local, &peer->srx, skb) < 0) + return NULL; b->peer_backlog[peer_tail] = NULL; smp_store_release(&b->peer_backlog_tail, (peer_tail + 1) & (RXRPC_BACKLOG_MAX - 1)); + + rxrpc_new_incoming_peer(local, peer); } /* Now allocate and set up the connection */ @@ -335,30 +332,16 @@ static struct rxrpc_call *rxrpc_alloc_incoming_call(struct rxrpc_sock *rx, * The call is returned with the user access mutex held. */ struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *local, + struct rxrpc_sock *rx, + struct rxrpc_peer *peer, struct rxrpc_connection *conn, struct sk_buff *skb) { struct rxrpc_skb_priv *sp = rxrpc_skb(skb); - struct rxrpc_sock *rx; struct rxrpc_call *call; - u16 service_id = sp->hdr.serviceId; _enter(""); - /* Get the socket providing the service */ - rx = rcu_dereference(local->service); - if (rx && (service_id == rx->srx.srx_service || - service_id == rx->second_service)) - goto found_service; - - trace_rxrpc_abort(0, "INV", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq, - RX_INVALID_OPERATION, EOPNOTSUPP); - skb->mark = RXRPC_SKB_MARK_REJECT_ABORT; - skb->priority = RX_INVALID_OPERATION; - _leave(" = NULL [service]"); - return NULL; - -found_service: spin_lock(&rx->incoming_lock); if (rx->sk.sk_state == RXRPC_SERVER_LISTEN_DISABLED || rx->sk.sk_state == RXRPC_CLOSE) { @@ -371,7 +354,7 @@ struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *local, goto out; } - call = rxrpc_alloc_incoming_call(rx, local, conn, skb); + call = rxrpc_alloc_incoming_call(rx, local, peer, conn, skb); if (!call) { skb->mark = RXRPC_SKB_MARK_REJECT_BUSY; _leave(" = NULL [busy]"); diff --git a/net/rxrpc/conn_object.c b/net/rxrpc/conn_object.c index 390ba50cfab4..b4438f98dc5c 100644 --- a/net/rxrpc/conn_object.c +++ b/net/rxrpc/conn_object.c @@ -69,10 +69,14 @@ struct rxrpc_connection *rxrpc_alloc_connection(gfp_t gfp) * If successful, a pointer to the connection is returned, but no ref is taken. * NULL is returned if there is no match. * + * When searching for a service call, if we find a peer but no connection, we + * return that through *_peer in case we need to create a new service call. + * * The caller must be holding the RCU read lock. */ struct rxrpc_connection *rxrpc_find_connection_rcu(struct rxrpc_local *local, - struct sk_buff *skb) + struct sk_buff *skb, + struct rxrpc_peer **_peer) { struct rxrpc_connection *conn; struct rxrpc_conn_proto k; @@ -104,6 +108,7 @@ struct rxrpc_connection *rxrpc_find_connection_rcu(struct rxrpc_local *local, peer = rxrpc_lookup_peer_rcu(local, &srx); if (!peer) goto not_found; + *_peer = peer; conn = rxrpc_find_service_conn_rcu(peer, skb); if (!conn || atomic_read(&conn->usage) == 0) goto not_found; diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c index a569e9e010d1..800f5b8a1baa 100644 --- a/net/rxrpc/input.c +++ b/net/rxrpc/input.c @@ -1128,7 +1128,8 @@ void rxrpc_data_ready(struct sock *udp_sk) struct rxrpc_call *call = NULL; struct rxrpc_skb_priv *sp; struct rxrpc_local *local = udp_sk->sk_user_data; - struct rxrpc_sock *rx; + struct rxrpc_peer *peer = NULL; + struct rxrpc_sock *rx = NULL; struct sk_buff *skb; unsigned int channel; int ret, skew = 0; @@ -1250,7 +1251,7 @@ void rxrpc_data_ready(struct sock *udp_sk) } } - conn = rxrpc_find_connection_rcu(local, skb); + conn = rxrpc_find_connection_rcu(local, skb, &peer); if (conn) { if (sp->hdr.securityIndex != conn->security_ix) goto wrong_security; @@ -1339,7 +1340,7 @@ void rxrpc_data_ready(struct sock *udp_sk) goto bad_message_unlock; if (sp->hdr.seq != 1) goto discard_unlock; - call = rxrpc_new_incoming_call(local, conn, skb); + call = rxrpc_new_incoming_call(local, rx, peer, conn, skb); if (!call) { rcu_read_unlock(); goto reject_packet; 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; } /*