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Subject[PATCH net] ice: Fix race condition during interface enslave
Date
Commit 5dbbbd01cbba83 ("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>
---
drivers/net/ethernet/intel/ice/ice.h | 11 ++++++++++-
drivers/net/ethernet/intel/ice/ice_main.c | 12 +++++++++++-
2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice.h b/drivers/net/ethernet/intel/ice/ice.h
index 3121f9b04f59..bea1d1e39fa2 100644
--- a/drivers/net/ethernet/intel/ice/ice.h
+++ b/drivers/net/ethernet/intel/ice/ice.h
@@ -898,7 +898,16 @@ static inline void ice_set_rdma_cap(struct ice_pf *pf)
*/
static inline void ice_clear_rdma_cap(struct ice_pf *pf)
{
- ice_unplug_aux_dev(pf);
+ /* We can directly unplug aux device here only if the flag bit
+ * ICE_FLAG_PLUG_AUX_DEV is not set because ice_unplug_aux_dev()
+ * could race with ice_plug_aux_dev() called from
+ * ice_service_task(). In this case we only clear that bit now and
+ * aux device will be unplugged later once ice_plug_aux_device()
+ * called from ice_service_task() finishes (see ice_service_task()).
+ */
+ if (!test_and_clear_bit(ICE_FLAG_PLUG_AUX_DEV, pf->flags))
+ ice_unplug_aux_dev(pf);
+
clear_bit(ICE_FLAG_RDMA_ENA, pf->flags);
clear_bit(ICE_FLAG_AUX_ENA, pf->flags);
}
diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
index 83e3e8aae6cf..493942e910be 100644
--- a/drivers/net/ethernet/intel/ice/ice_main.c
+++ b/drivers/net/ethernet/intel/ice/ice_main.c
@@ -2255,9 +2255,19 @@ static void ice_service_task(struct work_struct *work)
return;
}

- if (test_and_clear_bit(ICE_FLAG_PLUG_AUX_DEV, pf->flags))
+ if (test_bit(ICE_FLAG_PLUG_AUX_DEV, pf->flags)) {
+ /* Plug aux device per request */
ice_plug_aux_dev(pf);

+ /* Mark plugging as done but check whether unplug was
+ * requested during ice_plug_aux_dev() call
+ * (e.g. from ice_clear_rdma_cap()) and if so then
+ * plug aux device.
+ */
+ if (!test_and_clear_bit(ICE_FLAG_PLUG_AUX_DEV, pf->flags))
+ ice_unplug_aux_dev(pf);
+ }
+
if (test_and_clear_bit(ICE_FLAG_MTU_CHANGED, pf->flags)) {
struct iidc_event *event;

--
2.34.1
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