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rxrpc_find_service_conn_rcu: fix the usage of read_seqbegin_or_lock() 

[ 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>
This commit is contained in:
Oleg Nesterov 2023-11-17 17:48:46 +01:00 committed by Greg Kroah-Hartman
parent 08ade0fa61
commit 0cb7eafed5
1 changed files with 2 additions and 1 deletions
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3
net/rxrpc/conn_service.c
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@ -25,7 +25,7 @@ struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer,
struct rxrpc_conn_proto k; struct rxrpc_conn_proto k;
struct rxrpc_skb_priv *sp = rxrpc_skb(skb); struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
struct rb_node *p; struct rb_node *p;
unsigned int seq = 0; unsigned int seq = 1;
k.epoch = sp->hdr.epoch; k.epoch = sp->hdr.epoch;
k.cid = sp->hdr.cid & RXRPC_CIDMASK; 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 * under just the RCU read lock, so we have to check for
* changes. * changes.
*/ */
seq++; /* 2 on the 1st/lockless path, otherwise odd */
read_seqbegin_or_lock(&peer->service_conn_lock, &seq); read_seqbegin_or_lock(&peer->service_conn_lock, &seq);
p = rcu_dereference_raw(peer->service_conns.rb_node); p = rcu_dereference_raw(peer->service_conns.rb_node);