lkml.org 
[lkml]   [2022]   [Apr]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.19 13/53] rxrpc: Restore removed timer deletion
    Date
    From: David Howells <dhowells@redhat.com>

    [ Upstream commit ee3b0826b4764f6c13ad6db67495c5a1c38e9025 ]

    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: 1946014ca3b1 ("rxrpc: fix a race in rxrpc_exit_net()")
    Signed-off-by: David 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: Eric Dumazet <edumazet@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/rxrpc/net_ns.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/net/rxrpc/net_ns.c b/net/rxrpc/net_ns.c
    index 1b403c2573da..39579cfcf9b8 100644
    --- a/net/rxrpc/net_ns.c
    +++ b/net/rxrpc/net_ns.c
    @@ -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);
    --
    2.35.1


    \
     
     \ /
      Last update: 2022-04-26 10:38    [W:5.349 / U:0.152 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site