qede: fix NULL pointer deref in __qede_remove()

While rebooting the system with SR-IOV vfs enabled leads
to below crash due to recurrence of __qede_remove() on the VF
devices (first from .shutdown() flow of the VF itself and
another from PF's .shutdown() flow executing pci_disable_sriov())

This patch adds a safeguard in __qede_remove() flow to fix this,
so that driver doesn't attempt to remove "already removed" devices.

[  194.360134] BUG: unable to handle kernel NULL pointer dereference at 00000000000008dc
[  194.360227] IP: [<ffffffffc03553c4>] __qede_remove+0x24/0x130 [qede]
[  194.360304] PGD 0
[  194.360325] Oops: 0000 [#1] SMP
[  194.360360] Modules linked in: tcp_lp fuse tun bridge stp llc devlink bonding ip_set nfnetlink ib_isert iscsi_target_mod ib_srpt target_core_mod ib_srp scsi_transport_srp scsi_tgt ib_ipoib ib_umad rpcrdma sunrpc rdma_ucm ib_uverbs ib_iser rdma_cm iw_cm ib_cm libiscsi scsi_transport_iscsi dell_smbios iTCO_wdt iTCO_vendor_support dell_wmi_descriptor dcdbas vfat fat pcc_cpufreq skx_edac intel_powerclamp coretemp intel_rapl iosf_mbi kvm_intel kvm irqbypass crc32_pclmul ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd qedr ib_core pcspkr ses enclosure joydev ipmi_ssif sg i2c_i801 lpc_ich mei_me mei wmi ipmi_si ipmi_devintf ipmi_msghandler tpm_crb acpi_pad acpi_power_meter xfs libcrc32c sd_mod crc_t10dif crct10dif_generic crct10dif_pclmul crct10dif_common crc32c_intel mgag200
[  194.361044]  qede i2c_algo_bit drm_kms_helper qed syscopyarea sysfillrect nvme sysimgblt fb_sys_fops ttm nvme_core mpt3sas crc8 ptp drm pps_core ahci raid_class scsi_transport_sas libahci libata drm_panel_orientation_quirks nfit libnvdimm dm_mirror dm_region_hash dm_log dm_mod [last unloaded: ip_tables]
[  194.361297] CPU: 51 PID: 7996 Comm: reboot Kdump: loaded Not tainted 3.10.0-1062.el7.x86_64 #1
[  194.361359] Hardware name: Dell Inc. PowerEdge MX840c/0740HW, BIOS 2.4.6 10/15/2019
[  194.361412] task: ffff9cea9b360000 ti: ffff9ceabebdc000 task.ti: ffff9ceabebdc000
[  194.361463] RIP: 0010:[<ffffffffc03553c4>]  [<ffffffffc03553c4>] __qede_remove+0x24/0x130 [qede]
[  194.361534] RSP: 0018:ffff9ceabebdfac0  EFLAGS: 00010282
[  194.361570] RAX: 0000000000000000 RBX: ffff9cd013846098 RCX: 0000000000000000
[  194.361621] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff9cd013846098
[  194.361668] RBP: ffff9ceabebdfae8 R08: 0000000000000000 R09: 0000000000000000
[  194.361715] R10: 00000000bfe14201 R11: ffff9ceabfe141e0 R12: 0000000000000000
[  194.361762] R13: ffff9cd013846098 R14: 0000000000000000 R15: ffff9ceab5e48000
[  194.361810] FS:  00007f799c02d880(0000) GS:ffff9ceacb0c0000(0000) knlGS:0000000000000000
[  194.361865] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  194.361903] CR2: 00000000000008dc CR3: 0000001bdac76000 CR4: 00000000007607e0
[  194.361953] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  194.362002] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  194.362051] PKRU: 55555554
[  194.362073] Call Trace:
[  194.362109]  [<ffffffffc0355500>] qede_remove+0x10/0x20 [qede]
[  194.362180]  [<ffffffffb97d0f3e>] pci_device_remove+0x3e/0xc0
[  194.362240]  [<ffffffffb98b3c52>] __device_release_driver+0x82/0xf0
[  194.362285]  [<ffffffffb98b3ce3>] device_release_driver+0x23/0x30
[  194.362343]  [<ffffffffb97c86d4>] pci_stop_bus_device+0x84/0xa0
[  194.362388]  [<ffffffffb97c87e2>] pci_stop_and_remove_bus_device+0x12/0x20
[  194.362450]  [<ffffffffb97f153f>] pci_iov_remove_virtfn+0xaf/0x160
[  194.362496]  [<ffffffffb97f1aec>] sriov_disable+0x3c/0xf0
[  194.362534]  [<ffffffffb97f1bc3>] pci_disable_sriov+0x23/0x30
[  194.362599]  [<ffffffffc02f83c3>] qed_sriov_disable+0x5e3/0x650 [qed]
[  194.362658]  [<ffffffffb9622df6>] ? kfree+0x106/0x140
[  194.362709]  [<ffffffffc02cc0c0>] ? qed_free_stream_mem+0x70/0x90 [qed]
[  194.362754]  [<ffffffffb9622df6>] ? kfree+0x106/0x140
[  194.362803]  [<ffffffffc02cd659>] qed_slowpath_stop+0x1a9/0x1d0 [qed]
[  194.362854]  [<ffffffffc035544e>] __qede_remove+0xae/0x130 [qede]
[  194.362904]  [<ffffffffc03554e0>] qede_shutdown+0x10/0x20 [qede]
[  194.362956]  [<ffffffffb97cf90a>] pci_device_shutdown+0x3a/0x60
[  194.363010]  [<ffffffffb98b180b>] device_shutdown+0xfb/0x1f0
[  194.363066]  [<ffffffffb94b66c6>] kernel_restart_prepare+0x36/0x40
[  194.363107]  [<ffffffffb94b66e2>] kernel_restart+0x12/0x60
[  194.363146]  [<ffffffffb94b6959>] SYSC_reboot+0x229/0x260
[  194.363196]  [<ffffffffb95f200d>] ? handle_mm_fault+0x39d/0x9b0
[  194.363253]  [<ffffffffb942b621>] ? __switch_to+0x151/0x580
[  194.363304]  [<ffffffffb9b7ec28>] ? __schedule+0x448/0x9c0
[  194.363343]  [<ffffffffb94b69fe>] SyS_reboot+0xe/0x10
[  194.363387]  [<ffffffffb9b8bede>] system_call_fastpath+0x25/0x2a
[  194.363430] Code: f9 e9 37 ff ff ff 90 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 41 55 4c 8d af 98 00 00 00 41 54 4c 89 ef 41 89 f4 53 e8 4c e4 55 f9 <80> b8 dc 08 00 00 01 48 89 c3 4c 8d b8 c0 08 00 00 4c 8b b0 c0
[  194.363712] RIP  [<ffffffffc03553c4>] __qede_remove+0x24/0x130 [qede]
[  194.363764]  RSP <ffff9ceabebdfac0>
[  194.363791] CR2: 00000000000008dc

Signed-off-by: Manish Chopra <manishc@marvell.com>
Signed-off-by: Ariel Elior <aelior@marvell.com>
Signed-off-by: Sudarsana Kalluru <skalluru@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/qede/qede_main.c

@@ -1208,8 +1208,16 @@ enum qede_remove_mode {
 static void __qede_remove(struct pci_dev *pdev, enum qede_remove_mode mode)
 {
 	struct net_device *ndev = pci_get_drvdata(pdev);
-	struct qede_dev *edev = netdev_priv(ndev);
-	struct qed_dev *cdev = edev->cdev;
+	struct qede_dev *edev;
+	struct qed_dev *cdev;
+
+	if (!ndev) {
+		dev_info(&pdev->dev, "Device has already been removed\n");
+		return;
+	}
+
+	edev = netdev_priv(ndev);
+	cdev = edev->cdev;
 
 	DP_INFO(edev, "Starting qede_remove\n");