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Message-ID: <158072586542.743488.10326831447843659109.stgit@warthog.procyon.org.uk>
Date: Mon, 03 Feb 2020 10:31:05 +0000
From: David Howells <dhowells@...hat.com>
To: netdev@...r.kernel.org
Cc: dhowells@...hat.com, linux-afs@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: [PATCH net 3/4] rxrpc: Fix missing active use pinning of rxrpc_local
object ver #2
The introduction of a split between the reference count on rxrpc_local
objects and the usage count didn't quite go far enough. A number of kernel
work items need to make use of the socket to perform transmission. These
also need to get an active count on the local object to prevent the socket
from being closed.
Fix this by getting the active count in those places.
Also split out the raw active count get/put functions as these places tend
to hold refs on the rxrpc_local object already, so getting and putting an
extra object ref is just a waste of time.
The problem can lead to symptoms like:
BUG: kernel NULL pointer dereference, address: 0000000000000018
..
CPU: 2 PID: 818 Comm: kworker/u9:0 Not tainted 5.5.0-fscache+ #51
...
RIP: 0010:selinux_socket_sendmsg+0x5/0x13
...
Call Trace:
security_socket_sendmsg+0x2c/0x3e
sock_sendmsg+0x1a/0x46
rxrpc_send_keepalive+0x131/0x1ae
rxrpc_peer_keepalive_worker+0x219/0x34b
process_one_work+0x18e/0x271
worker_thread+0x1a3/0x247
kthread+0xe6/0xeb
ret_from_fork+0x1f/0x30
Fixes: 730c5fd42c1e ("rxrpc: Fix local endpoint refcounting")
Signed-off-by: David Howells <dhowells@...hat.com>
---
net/rxrpc/af_rxrpc.c | 2 ++
net/rxrpc/ar-internal.h | 10 ++++++++++
net/rxrpc/conn_event.c | 30 ++++++++++++++++++++----------
net/rxrpc/local_object.c | 18 +++++++-----------
net/rxrpc/peer_event.c | 42 +++++++++++++++++++++++-------------------
5 files changed, 62 insertions(+), 40 deletions(-)
diff --git a/net/rxrpc/af_rxrpc.c b/net/rxrpc/af_rxrpc.c
index 9d3c4d2d893a..fe42f986cd94 100644
--- a/net/rxrpc/af_rxrpc.c
+++ b/net/rxrpc/af_rxrpc.c
@@ -194,6 +194,7 @@ static int rxrpc_bind(struct socket *sock, struct sockaddr *saddr, int len)
service_in_use:
write_unlock(&local->services_lock);
rxrpc_unuse_local(local);
+ rxrpc_put_local(local);
ret = -EADDRINUSE;
error_unlock:
release_sock(&rx->sk);
@@ -899,6 +900,7 @@ static int rxrpc_release_sock(struct sock *sk)
rxrpc_purge_queue(&sk->sk_receive_queue);
rxrpc_unuse_local(rx->local);
+ rxrpc_put_local(rx->local);
rx->local = NULL;
key_put(rx->key);
rx->key = NULL;
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 5e99df80e80a..94441fee85bc 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -1021,6 +1021,16 @@ void rxrpc_unuse_local(struct rxrpc_local *);
void rxrpc_queue_local(struct rxrpc_local *);
void rxrpc_destroy_all_locals(struct rxrpc_net *);
+static inline bool __rxrpc_unuse_local(struct rxrpc_local *local)
+{
+ return atomic_dec_return(&local->active_users) == 0;
+}
+
+static inline bool __rxrpc_use_local(struct rxrpc_local *local)
+{
+ return atomic_fetch_add_unless(&local->active_users, 1, 0) != 0;
+}
+
/*
* misc.c
*/
diff --git a/net/rxrpc/conn_event.c b/net/rxrpc/conn_event.c
index 808a4723f868..06fcff2ebbba 100644
--- a/net/rxrpc/conn_event.c
+++ b/net/rxrpc/conn_event.c
@@ -438,16 +438,12 @@ static void rxrpc_process_delayed_final_acks(struct rxrpc_connection *conn)
/*
* connection-level event processor
*/
-void rxrpc_process_connection(struct work_struct *work)
+static void rxrpc_do_process_connection(struct rxrpc_connection *conn)
{
- struct rxrpc_connection *conn =
- container_of(work, struct rxrpc_connection, processor);
struct sk_buff *skb;
u32 abort_code = RX_PROTOCOL_ERROR;
int ret;
- rxrpc_see_connection(conn);
-
if (test_and_clear_bit(RXRPC_CONN_EV_CHALLENGE, &conn->events))
rxrpc_secure_connection(conn);
@@ -475,18 +471,32 @@ void rxrpc_process_connection(struct work_struct *work)
}
}
-out:
- rxrpc_put_connection(conn);
- _leave("");
return;
requeue_and_leave:
skb_queue_head(&conn->rx_queue, skb);
- goto out;
+ return;
protocol_error:
if (rxrpc_abort_connection(conn, ret, abort_code) < 0)
goto requeue_and_leave;
rxrpc_free_skb(skb, rxrpc_skb_freed);
- goto out;
+ return;
+}
+
+void rxrpc_process_connection(struct work_struct *work)
+{
+ struct rxrpc_connection *conn =
+ container_of(work, struct rxrpc_connection, processor);
+
+ rxrpc_see_connection(conn);
+
+ if (__rxrpc_use_local(conn->params.local)) {
+ rxrpc_do_process_connection(conn);
+ rxrpc_unuse_local(conn->params.local);
+ }
+
+ rxrpc_put_connection(conn);
+ _leave("");
+ return;
}
diff --git a/net/rxrpc/local_object.c b/net/rxrpc/local_object.c
index 3aa179efcda4..a6c1349e965d 100644
--- a/net/rxrpc/local_object.c
+++ b/net/rxrpc/local_object.c
@@ -383,14 +383,11 @@ void rxrpc_put_local(struct rxrpc_local *local)
*/
struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *local)
{
- unsigned int au;
-
local = rxrpc_get_local_maybe(local);
if (!local)
return NULL;
- au = atomic_fetch_add_unless(&local->active_users, 1, 0);
- if (au == 0) {
+ if (!__rxrpc_use_local(local)) {
rxrpc_put_local(local);
return NULL;
}
@@ -404,14 +401,11 @@ struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *local)
*/
void rxrpc_unuse_local(struct rxrpc_local *local)
{
- unsigned int au;
-
if (local) {
- au = atomic_dec_return(&local->active_users);
- if (au == 0)
+ if (__rxrpc_unuse_local(local)) {
+ rxrpc_get_local(local);
rxrpc_queue_local(local);
- else
- rxrpc_put_local(local);
+ }
}
}
@@ -468,7 +462,7 @@ static void rxrpc_local_processor(struct work_struct *work)
do {
again = false;
- if (atomic_read(&local->active_users) == 0) {
+ if (!__rxrpc_use_local(local)) {
rxrpc_local_destroyer(local);
break;
}
@@ -482,6 +476,8 @@ static void rxrpc_local_processor(struct work_struct *work)
rxrpc_process_local_events(local);
again = true;
}
+
+ __rxrpc_unuse_local(local);
} while (again);
rxrpc_put_local(local);
diff --git a/net/rxrpc/peer_event.c b/net/rxrpc/peer_event.c
index 48f67a9b1037..923b263c401b 100644
--- a/net/rxrpc/peer_event.c
+++ b/net/rxrpc/peer_event.c
@@ -364,27 +364,31 @@ static void rxrpc_peer_keepalive_dispatch(struct rxrpc_net *rxnet,
if (!rxrpc_get_peer_maybe(peer))
continue;
- spin_unlock_bh(&rxnet->peer_hash_lock);
-
- keepalive_at = peer->last_tx_at + RXRPC_KEEPALIVE_TIME;
- slot = keepalive_at - base;
- _debug("%02x peer %u t=%d {%pISp}",
- cursor, peer->debug_id, slot, &peer->srx.transport);
+ if (__rxrpc_use_local(peer->local)) {
+ spin_unlock_bh(&rxnet->peer_hash_lock);
+
+ keepalive_at = peer->last_tx_at + RXRPC_KEEPALIVE_TIME;
+ slot = keepalive_at - base;
+ _debug("%02x peer %u t=%d {%pISp}",
+ cursor, peer->debug_id, slot, &peer->srx.transport);
+
+ if (keepalive_at <= base ||
+ keepalive_at > base + RXRPC_KEEPALIVE_TIME) {
+ rxrpc_send_keepalive(peer);
+ slot = RXRPC_KEEPALIVE_TIME;
+ }
- if (keepalive_at <= base ||
- keepalive_at > base + RXRPC_KEEPALIVE_TIME) {
- rxrpc_send_keepalive(peer);
- slot = RXRPC_KEEPALIVE_TIME;
+ /* A transmission to this peer occurred since last we
+ * examined it so put it into the appropriate future
+ * bucket.
+ */
+ slot += cursor;
+ slot &= mask;
+ spin_lock_bh(&rxnet->peer_hash_lock);
+ list_add_tail(&peer->keepalive_link,
+ &rxnet->peer_keepalive[slot & mask]);
+ rxrpc_unuse_local(peer->local);
}
-
- /* A transmission to this peer occurred since last we examined
- * it so put it into the appropriate future bucket.
- */
- slot += cursor;
- slot &= mask;
- spin_lock_bh(&rxnet->peer_hash_lock);
- list_add_tail(&peer->keepalive_link,
- &rxnet->peer_keepalive[slot & mask]);
rxrpc_put_peer_locked(peer);
}
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