[Intel-wired-lan] [bug report] iavf: Fix deadlock in iavf_reset_task

[Dan Carpenter]

Hello Slawomir Laba,

The patch e85ff9c631e1: "iavf: Fix deadlock in iavf_reset_task" from
Feb 23, 2022, leads to the following Smatch static checker warning:

	drivers/net/ethernet/intel/iavf/iavf_main.c:2691 iavf_reset_task()
	error: double unlocked '&adapter->crit_lock' (orig line 2689)

drivers/net/ethernet/intel/iavf/iavf_main.c
    2613 static void iavf_reset_task(struct work_struct *work)
    2614 {
    2615         struct iavf_adapter *adapter = container_of(work,
    2616                                                       struct iavf_adapter,
    2617                                                       reset_task);
    2618         struct virtchnl_vf_resource *vfres = adapter->vf_res;
    2619         struct net_device *netdev = adapter->netdev;
    2620         struct iavf_hw *hw = &adapter->hw;
    2621         struct iavf_mac_filter *f, *ftmp;
    2622         struct iavf_cloud_filter *cf;
    2623         u32 reg_val;
    2624         int i = 0, err;
    2625         bool running;
    2626 
    2627         /* When device is being removed it doesn't make sense to run the reset
    2628          * task, just return in such a case.
    2629          */
    2630         if (!mutex_trylock(&adapter->crit_lock)) {
    2631                 if (adapter->state != __IAVF_REMOVE)
    2632                         queue_work(iavf_wq, &adapter->reset_task);
    2633 
    2634                 return;
    2635         }
    2636 
    2637         while (!mutex_trylock(&adapter->client_lock))
    2638                 usleep_range(500, 1000);
    2639         if (CLIENT_ENABLED(adapter)) {
    2640                 adapter->flags &= ~(IAVF_FLAG_CLIENT_NEEDS_OPEN |
    2641                                     IAVF_FLAG_CLIENT_NEEDS_CLOSE |
    2642                                     IAVF_FLAG_CLIENT_NEEDS_L2_PARAMS |
    2643                                     IAVF_FLAG_SERVICE_CLIENT_REQUESTED);
    2644                 cancel_delayed_work_sync(&adapter->client_task);
    2645                 iavf_notify_client_close(&adapter->vsi, true);
    2646         }
    2647         iavf_misc_irq_disable(adapter);
    2648         if (adapter->flags & IAVF_FLAG_RESET_NEEDED) {
    2649                 adapter->flags &= ~IAVF_FLAG_RESET_NEEDED;
    2650                 /* Restart the AQ here. If we have been reset but didn't
    2651                  * detect it, or if the PF had to reinit, our AQ will be hosed.
    2652                  */
    2653                 iavf_shutdown_adminq(hw);
    2654                 iavf_init_adminq(hw);
    2655                 iavf_request_reset(adapter);
    2656         }
    2657         adapter->flags |= IAVF_FLAG_RESET_PENDING;
    2658 
    2659         /* poll until we see the reset actually happen */
    2660         for (i = 0; i < IAVF_RESET_WAIT_DETECTED_COUNT; i++) {
    2661                 reg_val = rd32(hw, IAVF_VF_ARQLEN1) &
    2662                           IAVF_VF_ARQLEN1_ARQENABLE_MASK;
    2663                 if (!reg_val)
    2664                         break;
    2665                 usleep_range(5000, 10000);
    2666         }
    2667         if (i == IAVF_RESET_WAIT_DETECTED_COUNT) {
    2668                 dev_info(&adapter->pdev->dev, "Never saw reset\n");
    2669                 goto continue_reset; /* act like the reset happened */
    2670         }
    2671 
    2672         /* wait until the reset is complete and the PF is responding to us */
    2673         for (i = 0; i < IAVF_RESET_WAIT_COMPLETE_COUNT; i++) {
    2674                 /* sleep first to make sure a minimum wait time is met */
    2675                 msleep(IAVF_RESET_WAIT_MS);
    2676 
    2677                 reg_val = rd32(hw, IAVF_VFGEN_RSTAT) &
    2678                           IAVF_VFGEN_RSTAT_VFR_STATE_MASK;
    2679                 if (reg_val == VIRTCHNL_VFR_VFACTIVE)
    2680                         break;
    2681         }
    2682 
    2683         pci_set_master(adapter->pdev);
    2684         pci_restore_msi_state(adapter->pdev);
    2685 
    2686         if (i == IAVF_RESET_WAIT_COMPLETE_COUNT) {
    2687                 dev_err(&adapter->pdev->dev, "Reset never finished (%x)\n",
    2688                         reg_val);
    2689                 iavf_disable_vf(adapter);

The proble is that iavf_disable_vf() calls mutex_unlock(&adapter->crit_lock);

    2690                 mutex_unlock(&adapter->client_lock);
--> 2691                 mutex_unlock(&adapter->crit_lock);

so calling it again here is a bug.

I feel like I owe you an apology on this one because I asked you to add
the mutex_unlock() here via the kbuild-bot...  It is confusing though.
Does the unlock really need to be done inside iavf_disable_vf() are
can we move that to the callers?

    2692                 return; /* Do not attempt to reinit. It's dead, Jim. */
    2693         }
    2694 
    2695 continue_reset:
    2696         /* We don't use netif_running() because it may be true prior to
    2697          * ndo_open() returning, so we can't assume it means all our open
    2698          * tasks have finished, since we're not holding the rtnl_lock here.
    2699          */

regards,
dan carpenter