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SubjectRE: [PATCH net] ice: Fix race condition during interface enslave
Date
> -----Original Message-----
> From: Ivan Vecera <ivecera@redhat.com>
> Sent: Thursday, March 10, 2022 9:17 AM
> To: netdev@vger.kernel.org
> Cc: Petr Oros <poros@redhat.com>; Brandeburg, Jesse
> <jesse.brandeburg@intel.com>; Nguyen, Anthony L
> <anthony.l.nguyen@intel.com>; David S. Miller <davem@davemloft.net>;
> Jakub Kicinski <kuba@kernel.org>; moderated list:INTEL ETHERNET DRIVERS
> <intel-wired-lan@lists.osuosl.org>; open list <linux-kernel@vger.kernel.org>
> Subject: [PATCH net] ice: Fix race condition during interface enslave
>
> 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

This only addresses one case of unplugging the auxiliary bus. Rather than controlling one instance of
calling ice_unplig_aux_dev(), it seems like it would be better to modify ice_unplug_aux_dev so that it
will pause until any plugging is done by the service task (check for the pf->flag bit and wait until it clears
before progressing).

This way resets, devlink calls, etc would also be controlled from runaway plugging / unplugging of the aux
devices. This would eliminate the second check in the service task also, since unplug would not be allowed
to progress until the bit is cleared by the service task.

In an upcoming patch I am making all plugging of the aux devices done in the service task, this would centralize
it and protect it against looping plug/unplug of the auxiliary devices.

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