From: David Howells dhowells@redhat.com
[ Upstream commit 3bcd6c7eaa53b56c3f584da46a1f7652e759d0e5 ]
After rxrpc_unbundle_conn() has removed a connection from a bundle, it checks to see if there are any conns with available channels and, if not, removes and attempts to destroy the bundle.
Whilst it does check after grabbing client_bundles_lock that there are no connections attached, this races with rxrpc_look_up_bundle() retrieving the bundle, but not attaching a connection for the connection to be attached later.
There is therefore a window in which the bundle can get destroyed before we manage to attach a new connection to it.
Fix this by adding an "active" counter to struct rxrpc_bundle:
(1) rxrpc_connect_call() obtains an active count by prepping/looking up a bundle and ditches it before returning.
(2) If, during rxrpc_connect_call(), a connection is added to the bundle, this obtains an active count, which is held until the connection is discarded.
(3) rxrpc_deactivate_bundle() is created to drop an active count on a bundle and destroy it when the active count reaches 0. The active count is checked inside client_bundles_lock() to prevent a race with rxrpc_look_up_bundle().
(4) rxrpc_unbundle_conn() then calls rxrpc_deactivate_bundle().
Fixes: 245500d853e9 ("rxrpc: Rewrite the client connection manager") Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-15975 Signed-off-by: David Howells dhowells@redhat.com Tested-by: zdi-disclosures@trendmicro.com cc: Marc Dionne marc.dionne@auristor.com cc: linux-afs@lists.infradead.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/rxrpc/ar-internal.h | 1 + net/rxrpc/conn_client.c | 38 +++++++++++++++++++++++--------------- 2 files changed, 24 insertions(+), 15 deletions(-)
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index 62c70709d798..e0123efa2a62 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -399,6 +399,7 @@ enum rxrpc_conn_proto_state { struct rxrpc_bundle { struct rxrpc_conn_parameters params; refcount_t ref; + atomic_t active; /* Number of active users */ unsigned int debug_id; bool try_upgrade; /* True if the bundle is attempting upgrade */ bool alloc_conn; /* True if someone's getting a conn */ diff --git a/net/rxrpc/conn_client.c b/net/rxrpc/conn_client.c index 3c9eeb5b750c..bdb335cb2d05 100644 --- a/net/rxrpc/conn_client.c +++ b/net/rxrpc/conn_client.c @@ -40,6 +40,8 @@ __read_mostly unsigned long rxrpc_conn_idle_client_fast_expiry = 2 * HZ; DEFINE_IDR(rxrpc_client_conn_ids); static DEFINE_SPINLOCK(rxrpc_conn_id_lock);
+static void rxrpc_deactivate_bundle(struct rxrpc_bundle *bundle); + /* * Get a connection ID and epoch for a client connection from the global pool. * The connection struct pointer is then recorded in the idr radix tree. The @@ -123,6 +125,7 @@ static struct rxrpc_bundle *rxrpc_alloc_bundle(struct rxrpc_conn_parameters *cp, bundle->params = *cp; rxrpc_get_peer(bundle->params.peer); refcount_set(&bundle->ref, 1); + atomic_set(&bundle->active, 1); spin_lock_init(&bundle->channel_lock); INIT_LIST_HEAD(&bundle->waiting_calls); } @@ -149,7 +152,7 @@ void rxrpc_put_bundle(struct rxrpc_bundle *bundle)
dead = __refcount_dec_and_test(&bundle->ref, &r);
- _debug("PUT B=%x %d", d, r); + _debug("PUT B=%x %d", d, r - 1); if (dead) rxrpc_free_bundle(bundle); } @@ -338,6 +341,7 @@ static struct rxrpc_bundle *rxrpc_look_up_bundle(struct rxrpc_conn_parameters *c rxrpc_free_bundle(candidate); found_bundle: rxrpc_get_bundle(bundle); + atomic_inc(&bundle->active); spin_unlock(&local->client_bundles_lock); _leave(" = %u [found]", bundle->debug_id); return bundle; @@ -435,6 +439,7 @@ static void rxrpc_add_conn_to_bundle(struct rxrpc_bundle *bundle, gfp_t gfp) if (old) trace_rxrpc_client(old, -1, rxrpc_client_replace); candidate->bundle_shift = shift; + atomic_inc(&bundle->active); bundle->conns[i] = candidate; for (j = 0; j < RXRPC_MAXCALLS; j++) set_bit(shift + j, &bundle->avail_chans); @@ -725,6 +730,7 @@ int rxrpc_connect_call(struct rxrpc_sock *rx, smp_rmb();
out_put_bundle: + rxrpc_deactivate_bundle(bundle); rxrpc_put_bundle(bundle); out: _leave(" = %d", ret); @@ -900,9 +906,8 @@ void rxrpc_disconnect_client_call(struct rxrpc_bundle *bundle, struct rxrpc_call static void rxrpc_unbundle_conn(struct rxrpc_connection *conn) { struct rxrpc_bundle *bundle = conn->bundle; - struct rxrpc_local *local = bundle->params.local; unsigned int bindex; - bool need_drop = false, need_put = false; + bool need_drop = false; int i;
_enter("C=%x", conn->debug_id); @@ -921,15 +926,22 @@ static void rxrpc_unbundle_conn(struct rxrpc_connection *conn) } spin_unlock(&bundle->channel_lock);
- /* If there are no more connections, remove the bundle */ - if (!bundle->avail_chans) { - _debug("maybe unbundle"); - spin_lock(&local->client_bundles_lock); + if (need_drop) { + rxrpc_deactivate_bundle(bundle); + rxrpc_put_connection(conn); + } +}
- for (i = 0; i < ARRAY_SIZE(bundle->conns); i++) - if (bundle->conns[i]) - break; - if (i == ARRAY_SIZE(bundle->conns) && !bundle->params.exclusive) { +/* + * Drop the active count on a bundle. + */ +static void rxrpc_deactivate_bundle(struct rxrpc_bundle *bundle) +{ + struct rxrpc_local *local = bundle->params.local; + bool need_put = false; + + if (atomic_dec_and_lock(&bundle->active, &local->client_bundles_lock)) { + if (!bundle->params.exclusive) { _debug("erase bundle"); rb_erase(&bundle->local_node, &local->client_bundles); need_put = true; @@ -939,10 +951,6 @@ static void rxrpc_unbundle_conn(struct rxrpc_connection *conn) if (need_put) rxrpc_put_bundle(bundle); } - - if (need_drop) - rxrpc_put_connection(conn); - _leave(""); }
/*