Commit d85d7382 authored by David Howells's avatar David Howells Committed by Cai Xinchen
Browse files

rxrpc: Restore removed timer deletion 

stable inclusion
from stable-v4.19.240
commit bf042aa56e2a432b694a1286a290ae11c8e6c685
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBP6Y3
CVE: CVE-2022-49087

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bf042aa56e2a432b694a1286a290ae11c8e6c685



--------------------------------

[ Upstream commit ee3b0826 ]

A recent patch[1] from Eric Dumazet flipped the order in which the
keepalive timer and the keepalive worker were cancelled in order to fix a
syzbot reported issue[2].  Unfortunately, this enables the mirror image bug
whereby the timer races with rxrpc_exit_net(), restarting the worker after
it has been cancelled:

	CPU 1		CPU 2
	===============	=====================
			if (rxnet->live)
			<INTERRUPT>
	rxnet->live = false;
 	cancel_work_sync(&rxnet->peer_keepalive_work);
			rxrpc_queue_work(&rxnet->peer_keepalive_work);
	del_timer_sync(&rxnet->peer_keepalive_timer);

Fix this by restoring the removed del_timer_sync() so that we try to remove
the timer twice.  If the timer runs again, it should see ->live == false
and not restart the worker.

Fixes: 1946014c ("rxrpc: fix a race in rxrpc_exit_net()")
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
cc: Eric Dumazet <edumazet@google.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/20220404183439.3537837-1-eric.dumazet@gmail.com/ [1]
Link: https://syzkaller.appspot.com/bug?extid=724378c4bb58f703b09a

 [2]
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarCai Xinchen <caixinchen1@huawei.com>
parent 0a71d147

net/rxrpc/net_ns.c

+2 −0
Original line number Diff line number Diff line
@@ -117,7 +117,9 @@ static __net_exit void rxrpc_exit_net(struct net *net) 
	struct rxrpc_net *rxnet = rxrpc_net(net);



	rxnet->live = false;

	del_timer_sync(&rxnet->peer_keepalive_timer);

	cancel_work_sync(&rxnet->peer_keepalive_work);

	/* Remove the timer again as the worker may have restarted it. */

	del_timer_sync(&rxnet->peer_keepalive_timer);

	rxrpc_destroy_all_calls(rxnet);

	rxrpc_destroy_all_connections(rxnet);