ice: fix NULL pointer dereference in ice_unplug_aux_dev() on reset

Issuing a reset when the driver is loaded without RDMA support, will
results in a crash as it attempts to remove RDMA's non-existent auxbus
device:
echo 1 > /sys/class/net/<if>/device/reset

BUG: kernel NULL pointer dereference, address: 0000000000000008
...
RIP: 0010:ice_unplug_aux_dev+0x29/0x70 [ice]
...
Call Trace:
<TASK>
ice_prepare_for_reset+0x77/0x260 [ice]
pci_dev_save_and_disable+0x2c/0x70
pci_reset_function+0x88/0x130
reset_store+0x5a/0xa0
kernfs_fop_write_iter+0x15e/0x210
vfs_write+0x273/0x520
ksys_write+0x6b/0xe0
do_syscall_64+0x79/0x3b0
entry_SYSCALL_64_after_hwframe+0x76/0x7e

ice_unplug_aux_dev() checks pf->cdev_info->adev for NULL pointer, but
pf->cdev_info will also be NULL, leading to the deref in the trace above.

Introduce a flag to be set when the creation of the auxbus device is
successful, to avoid multiple NULL pointer checks in ice_unplug_aux_dev().

Fixes: c24a65b ("iidc/ice/irdma: Update IDC to support multiple consumers")
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Author: etantilov

drivers/net/ethernet/intel/ice/ice.h

@@ -510,6 +510,7 @@ enum ice_pf_flags {
 	ICE_FLAG_LINK_LENIENT_MODE_ENA,
 	ICE_FLAG_PLUG_AUX_DEV,
 	ICE_FLAG_UNPLUG_AUX_DEV,
+	ICE_FLAG_AUX_DEV_CREATED,
 	ICE_FLAG_MTU_CHANGED,
 	ICE_FLAG_GNSS,			/* GNSS successfully initialized */
 	ICE_FLAG_DPLL,			/* SyncE/PTP dplls initialized */

drivers/net/ethernet/intel/ice/ice_idc.c

@@ -336,6 +336,7 @@ int ice_plug_aux_dev(struct ice_pf *pf)
 	mutex_lock(&pf->adev_mutex);
 	cdev->adev = adev;
 	mutex_unlock(&pf->adev_mutex);
+	set_bit(ICE_FLAG_AUX_DEV_CREATED, pf->flags);
 
 	return 0;
 }
@@ -347,15 +348,16 @@ void ice_unplug_aux_dev(struct ice_pf *pf)
 {
 	struct auxiliary_device *adev;
 
+	if (!test_and_clear_bit(ICE_FLAG_AUX_DEV_CREATED, pf->flags))
+		return;
+
 	mutex_lock(&pf->adev_mutex);
 	adev = pf->cdev_info->adev;
 	pf->cdev_info->adev = NULL;
 	mutex_unlock(&pf->adev_mutex);
 
-	if (adev) {
-		auxiliary_device_delete(adev);
-		auxiliary_device_uninit(adev);
-	}
+	auxiliary_device_delete(adev);
+	auxiliary_device_uninit(adev);
 }
 
 /**