Messages in this thread Patch in this message | | | From | Ilya Dryomov <> | Date | Mon, 14 Jan 2019 21:37:25 +0100 | Subject | Re: [PATCH] libceph: protect pending flags in ceph_con_keepalive() |
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On Thu, Jan 3, 2019 at 4:50 AM Myungho Jung <mhjungk@gmail.com> wrote: > I reproduced on vm using syzkaller utils and verified the fix by syzbot.
Hi Myungho,
I think this might be a better fix:
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c index d5718284db57..c5f5313e3537 100644 --- a/net/ceph/messenger.c +++ b/net/ceph/messenger.c @@ -3205,10 +3205,11 @@ void ceph_con_keepalive(struct ceph_connection *con) { dout("con_keepalive %p\n", con); mutex_lock(&con->mutex); + con_flag_set(con, CON_FLAG_KEEPALIVE_PENDING); clear_standby(con); mutex_unlock(&con->mutex); - if (con_flag_test_and_set(con, CON_FLAG_KEEPALIVE_PENDING) == 0 && - con_flag_test_and_set(con, CON_FLAG_WRITE_PENDING) == 0) + + if (con_flag_test_and_set(con, CON_FLAG_WRITE_PENDING) == 0) queue_con(con); } EXPORT_SYMBOL(ceph_con_keepalive); WRITE_PENDING can be set without con->mutex held from socket callbacks. This is the reason we use atomic bit ops here, so testing WRITE_PENDING under the lock didn't make sense to me.
At the same time, KEEPALIVE_PENDING could have been a non-atomic flag. I spent some time trying to make sense of conditioning queue_con() call on the previous value of KEEPALIVE_PENDING and couldn't see any, so I'm setting it with con_flag_set(), making ceph_con_keepalive() symmetric with ceph_con_send().
Thanks,
Ilya
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