Commit 5dbbbd01cb ("ice: Avoid RTNL lock when re-creating
auxiliary device") changes a process of re-creation of aux device
so ice_plug_aux_dev() is called from ice_service_task() context.
This unfortunately opens a race window that can result in dead-lock
when interface has left LAG and immediately enters LAG again.
Reproducer:
```
#!/bin/sh
ip link add lag0 type bond mode 1 miimon 100
ip link set lag0
for n in {1..10}; do
echo Cycle: $n
ip link set ens7f0 master lag0
sleep 1
ip link set ens7f0 nomaster
done
```
This results in:
[20976.208697] Workqueue: ice ice_service_task [ice]
[20976.213422] Call Trace:
[20976.215871] __schedule+0x2d1/0x830
[20976.219364] schedule+0x35/0xa0
[20976.222510] schedule_preempt_disabled+0xa/0x10
[20976.227043] __mutex_lock.isra.7+0x310/0x420
[20976.235071] enum_all_gids_of_dev_cb+0x1c/0x100 [ib_core]
[20976.251215] ib_enum_roce_netdev+0xa4/0xe0 [ib_core]
[20976.256192] ib_cache_setup_one+0x33/0xa0 [ib_core]
[20976.261079] ib_register_device+0x40d/0x580 [ib_core]
[20976.266139] irdma_ib_register_device+0x129/0x250 [irdma]
[20976.281409] irdma_probe+0x2c1/0x360 [irdma]
[20976.285691] auxiliary_bus_probe+0x45/0x70
[20976.289790] really_probe+0x1f2/0x480
[20976.298509] driver_probe_device+0x49/0xc0
[20976.302609] bus_for_each_drv+0x79/0xc0
[20976.306448] __device_attach+0xdc/0x160
[20976.310286] bus_probe_device+0x9d/0xb0
[20976.314128] device_add+0x43c/0x890
[20976.321287] __auxiliary_device_add+0x43/0x60
[20976.325644] ice_plug_aux_dev+0xb2/0x100 [ice]
[20976.330109] ice_service_task+0xd0c/0xed0 [ice]
[20976.342591] process_one_work+0x1a7/0x360
[20976.350536] worker_thread+0x30/0x390
[20976.358128] kthread+0x10a/0x120
[20976.365547] ret_from_fork+0x1f/0x40
...
[20976.438030] task:ip state:D stack: 0 pid:213658 ppid:213627 flags:0x00004084
[20976.446469] Call Trace:
[20976.448921] __schedule+0x2d1/0x830
[20976.452414] schedule+0x35/0xa0
[20976.455559] schedule_preempt_disabled+0xa/0x10
[20976.460090] __mutex_lock.isra.7+0x310/0x420
[20976.464364] device_del+0x36/0x3c0
[20976.467772] ice_unplug_aux_dev+0x1a/0x40 [ice]
[20976.472313] ice_lag_event_handler+0x2a2/0x520 [ice]
[20976.477288] notifier_call_chain+0x47/0x70
[20976.481386] __netdev_upper_dev_link+0x18b/0x280
[20976.489845] bond_enslave+0xe05/0x1790 [bonding]
[20976.494475] do_setlink+0x336/0xf50
[20976.502517] __rtnl_newlink+0x529/0x8b0
[20976.543441] rtnl_newlink+0x43/0x60
[20976.546934] rtnetlink_rcv_msg+0x2b1/0x360
[20976.559238] netlink_rcv_skb+0x4c/0x120
[20976.563079] netlink_unicast+0x196/0x230
[20976.567005] netlink_sendmsg+0x204/0x3d0
[20976.570930] sock_sendmsg+0x4c/0x50
[20976.574423] ____sys_sendmsg+0x1eb/0x250
[20976.586807] ___sys_sendmsg+0x7c/0xc0
[20976.606353] __sys_sendmsg+0x57/0xa0
[20976.609930] do_syscall_64+0x5b/0x1a0
[20976.613598] entry_SYSCALL_64_after_hwframe+0x65/0xca
1. Command 'ip link ... set nomaster' causes that ice_plug_aux_dev()
is called from ice_service_task() context, aux device is created
and associated device->lock is taken.
2. Command 'ip link ... set master...' calls ice's notifier under
RTNL lock and that notifier calls ice_unplug_aux_dev(). That
function tries to take aux device->lock but this is already taken
by ice_plug_aux_dev() in step 1
3. Later ice_plug_aux_dev() tries to take RTNL lock but this is already
taken in step 2
4. Dead-lock
The patch fixes this issue by following changes:
- Bit ICE_FLAG_PLUG_AUX_DEV is kept to be set during ice_plug_aux_dev()
call in ice_service_task()
- The bit is checked in ice_clear_rdma_cap() and only if it is not set
then ice_unplug_aux_dev() is called. If it is set (in other words
plugging of aux device was requested and ice_plug_aux_dev() is
potentially running) then the function only clears the bit
- Once ice_plug_aux_dev() call (in ice_service_task) is finished
the bit ICE_FLAG_PLUG_AUX_DEV is cleared but it is also checked
whether it was already cleared by ice_clear_rdma_cap(). If so then
aux device is unplugged.
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Co-developed-by: Petr Oros <poros@redhat.com>
Signed-off-by: Petr Oros <poros@redhat.com>
Reviewed-by: Dave Ertman <david.m.ertman@intel.com>
Link: https://lore.kernel.org/r/20220310171641.3863659-1-ivecera@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
5cb1ebdbc4