[PATCH AUTOSEL 5.4 10/12] rxrpc_find_service_conn_rcu: fix the usage of read_seqbegin_or_lock()
From: Sasha Levin <sashal@kernel.org>
Date: 2024-01-16 00:28:01
Also in:
lkml, stable
Subsystem:
networking [general], rxrpc sockets (af_rxrpc), the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Howells, Marc Dionne, Linus Torvalds
From: Oleg Nesterov <oleg@redhat.com> [ Upstream commit bad1a11c0f061aa073bab785389fe04f19ba02e1 ] rxrpc_find_service_conn_rcu() should make the "seq" counter odd on the second pass, otherwise read_seqbegin_or_lock() never takes the lock. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: David Howells <dhowells@redhat.com> cc: Marc Dionne <marc.dionne@auristor.com> cc: linux-afs@lists.infradead.org Link: https://lore.kernel.org/r/20231117164846.GA10410@redhat.com/ (local) Signed-off-by: Sasha Levin <sashal@kernel.org> --- net/rxrpc/conn_service.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/rxrpc/conn_service.c b/net/rxrpc/conn_service.c
index 21da48e3d2e5..7ad4b4e9341e 100644
--- a/net/rxrpc/conn_service.c
+++ b/net/rxrpc/conn_service.c@@ -25,7 +25,7 @@ struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer, struct rxrpc_conn_proto k; struct rxrpc_skb_priv *sp = rxrpc_skb(skb); struct rb_node *p; - unsigned int seq = 0; + unsigned int seq = 1; k.epoch = sp->hdr.epoch; k.cid = sp->hdr.cid & RXRPC_CIDMASK;
@@ -35,6 +35,7 @@ struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer, * under just the RCU read lock, so we have to check for * changes. */ + seq++; /* 2 on the 1st/lockless path, otherwise odd */ read_seqbegin_or_lock(&peer->service_conn_lock, &seq); p = rcu_dereference_raw(peer->service_conns.rb_node);
--
2.43.0