rbd: flush rbd_dev->watch_dwork after watch is unregistered
There is a problem if we are going to unmap a rbd device and the
watch_dwork is going to queue delayed work for watch:
unmap Thread watch Thread timer
do_rbd_remove
cancel_tasks_sync(rbd_dev)
queue_delayed_work for watch
destroy_workqueue(rbd_dev->task_wq)
drain_workqueue(wq)
destroy other resources in wq
call_timer_fn
__queue_work()
Then the delayed work escape the cancel_tasks_sync() and
destroy_workqueue() and we will get an user-after-free call trace:
BUG: unable to handle kernel NULL pointer dereference at
0000000000000000
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
Modules linked in:
CPU: 7 PID: 0 Comm: swapper/7 Tainted: G OE 4.17.0-rc6+ #13
Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
RIP: 0010:__queue_work+0x6a/0x3b0
RSP: 0018:
ffff9427df1c3e90 EFLAGS:
00010086
RAX:
ffff9427deca8400 RBX:
0000000000000000 RCX:
0000000000000000
RDX:
ffff9427deca8400 RSI:
ffff9427df1c3e50 RDI:
0000000000000000
RBP:
ffff942783e39e00 R08:
ffff9427deca8400 R09:
ffff9427df1c3f00
R10:
0000000000000004 R11:
0000000000000005 R12:
ffff9427cfb85970
R13:
0000000000002000 R14:
000000000001eca0 R15:
0000000000000007
FS:
0000000000000000(0000) GS:
ffff9427df1c0000(0000) knlGS:
0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
CR2:
0000000000000000 CR3:
00000004c900a005 CR4:
00000000000206e0
Call Trace:
<IRQ>
? __queue_work+0x3b0/0x3b0
call_timer_fn+0x2d/0x130
run_timer_softirq+0x16e/0x430
? tick_sched_timer+0x37/0x70
__do_softirq+0xd2/0x280
irq_exit+0xd5/0xe0
smp_apic_timer_interrupt+0x6c/0x130
apic_timer_interrupt+0xf/0x20
[ Move rbd_dev->watch_dwork cancellation so that rbd_reregister_watch()
either bails out early because the watch is UNREGISTERED at that point
or just gets cancelled. ]
Cc: stable@vger.kernel.org
Fixes: 99d1694310df ("rbd: retry watch re-registration periodically")
Signed-off-by: Dongsheng Yang <dongsheng.yang@easystack.cn>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>