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rxrpc_find_service_conn_rcu: fix the usage of read_seqbegin_or_lock()
author
Oleg Nesterov
<oleg@redhat.com>
Fri, 17 Nov 2023 16:48:46 +0000
(17:48 +0100)
committer
Greg Kroah-Hartman
<gregkh@linuxfoundation.org>
Mon, 5 Feb 2024 20:14:16 +0000
(20:14 +0000)
[ 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/
Signed-off-by: Sasha Levin <sashal@kernel.org>
net/rxrpc/conn_service.c
patch
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diff --git
a/net/rxrpc/conn_service.c
b/net/rxrpc/conn_service.c
index
89ac05a
..
39c908a
100644
(file)
--- 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);