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Message-ID: <20240116002731.216549-10-sashal@kernel.org>
Date: Mon, 15 Jan 2024 19:27:16 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
stable@...r.kernel.org
Cc: Oleg Nesterov <oleg@...hat.com>,
David Howells <dhowells@...hat.com>,
Marc Dionne <marc.dionne@...istor.com>,
linux-afs@...ts.infradead.org,
Sasha Levin <sashal@...nel.org>,
davem@...emloft.net,
edumazet@...gle.com,
kuba@...nel.org,
pabeni@...hat.com,
netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 10/12] rxrpc_find_service_conn_rcu: fix the usage of read_seqbegin_or_lock()
From: Oleg Nesterov <oleg@...hat.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@...hat.com>
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Marc Dionne <marc.dionne@...istor.com>
cc: linux-afs@...ts.infradead.org
Link: https://lore.kernel.org/r/20231117164846.GA10410@redhat.com/
Signed-off-by: Sasha Levin <sashal@...nel.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
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