4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov <oleg@xxxxxxxxxx> [ 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@xxxxxxxxxx> Signed-off-by: David Howells <dhowells@xxxxxxxxxx> cc: Marc Dionne <marc.dionne@xxxxxxxxxxxx> cc: linux-afs@xxxxxxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/20231117164846.GA10410@xxxxxxxxxx/ Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 6da7c4bf15e8..4b1564824aed 100644 --- a/net/rxrpc/conn_service.c +++ b/net/rxrpc/conn_service.c @@ -29,7 +29,7 @@ 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; @@ -39,6 +39,7 @@ 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
