RE: [Intel-wired-lan] [PATCH v2] igb: reinit_locked() should be called with rtnl_lock

[Brown, Aaron F]

> From: Intel-wired-lan <intel-wired-lan-bounces@xxxxxxxxxx> On Behalf Of
> Francesco Ruggeri
> Sent: Thursday, July 2, 2020 3:39 PM
> To: linux-kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; intel-wired-
> lan@xxxxxxxxxxxxxxxx; kuba@xxxxxxxxxx; davem@xxxxxxxxxxxxx; Kirsher, Jeffrey
> T <jeffrey.t.kirsher@xxxxxxxxx>; fruggeri@xxxxxxxxxx
> Subject: [Intel-wired-lan] [PATCH v2] igb: reinit_locked() should be called with
> rtnl_lock
> 
> We observed two panics involving races with igb_reset_task.
> The first panic is caused by this race condition:
> 
> 	kworker			reboot -f
> 
> 	igb_reset_task
> 	igb_reinit_locked
> 	igb_down
> 	napi_synchronize
> 				__igb_shutdown
> 				igb_clear_interrupt_scheme
> 				igb_free_q_vectors
> 				igb_free_q_vector
> 				adapter->q_vector[v_idx] = NULL;
> 	napi_disable
> 	Panics trying to access
> 	adapter->q_vector[v_idx].napi_state
> 
> The second panic (a divide error) is caused by this race:
> 
> kworker		reboot -f	tx packet
> 
> igb_reset_task
> 		__igb_shutdown
> 		rtnl_lock()
> 		...
> 		igb_clear_interrupt_scheme
> 		igb_free_q_vectors
> 		adapter->num_tx_queues = 0
> 		...
> 		rtnl_unlock()
> rtnl_lock()
> igb_reinit_locked
> igb_down
> igb_up
> netif_tx_start_all_queues
> 				dev_hard_start_xmit
> 				igb_xmit_frame
> 				igb_tx_queue_mapping
> 				Panics on
> 				r_idx % adapter->num_tx_queues
> 
> This commit applies to igb_reset_task the same changes that
> were applied to ixgbe in commit 2f90b8657ec9 ("ixgbe: this patch
> adds support for DCB to the kernel and ixgbe driver"),
> commit 8f4c5c9fb87a ("ixgbe: reinit_locked() should be called with
> rtnl_lock") and commit 88adce4ea8f9 ("ixgbe: fix possible race in
> reset subtask").
> 
> v2: add fix for second race condition above.
> 
> Signed-off-by: Francesco Ruggeri <fruggeri@xxxxxxxxxx>
> 
> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
Tested-by: Aaron Brown <aaron.f.brown@xxxxxxxxx>