[PATCH net 3/5] rxrpc: Fix locking issues with the peer record hash

[David Howells <dhowells@redhat.com>]

rxrpc_new_incoming_peer() can't use spin_lock_bh() whilst its caller has
interrupts disabled.

    WARNING: CPU: 0 PID: 1550 at kernel/softirq.c:369 __local_bh_enable_ip+0x46/0xd0
    ...
    Call Trace:
     rxrpc_alloc_incoming_call+0x1b0/0x400
     rxrpc_new_incoming_call+0x1dd/0x5e0
     rxrpc_input_packet+0x84a/0x920
     rxrpc_io_thread+0x40d/0xb40
     kthread+0x2ec/0x300
     ret_from_fork+0x24/0x40
     ret_from_fork_asm+0x1a/0x30
     </TASK>
    irq event stamp: 1811
    hardirqs last  enabled at (1809): _raw_spin_unlock_irq+0x24/0x50
    hardirqs last disabled at (1810): _raw_read_lock_irq+0x17/0x70
    softirqs last  enabled at (1182): handle_softirqs+0x3ee/0x430
    softirqs last disabled at (1811): rxrpc_new_incoming_peer+0x56/0x120

Fix this by using a plain spin_lock() instead.  IRQs are held, so softirqs
can't happen.

Fixes: a2ea9a907260 ("rxrpc: Use irq-disabling spinlocks between app and I/O thread")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: netdev@vger.kernel.org
---
 net/rxrpc/peer_object.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c
index 2ddc8ed68742..56e09d161a97 100644
--- a/net/rxrpc/peer_object.c
+++ b/net/rxrpc/peer_object.c
@@ -324,10 +324,10 @@ void rxrpc_new_incoming_peer(struct rxrpc_local *local, struct rxrpc_peer *peer)
 	hash_key = rxrpc_peer_hash_key(local, &peer->srx);
 	rxrpc_init_peer(local, peer, hash_key);
 
-	spin_lock_bh(&rxnet->peer_hash_lock);
+	spin_lock(&rxnet->peer_hash_lock);
 	hash_add_rcu(rxnet->peer_hash, &peer->hash_link, hash_key);
 	list_add_tail(&peer->keepalive_link, &rxnet->peer_keepalive_new);
-	spin_unlock_bh(&rxnet->peer_hash_lock);
+	spin_unlock(&rxnet->peer_hash_lock);
 }
 
 /*