ixgbe: Avoid NULL pointer dereference with VF on non-IPsec hw

An ipsec structure will not be allocated if the hardware does not support
offload. Fixes the following Oops:

[  191.045452] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[  191.054232] Mem abort info:
[  191.057014]   ESR = 0x96000004
[  191.060057]   Exception class = DABT (current EL), IL = 32 bits
[  191.065963]   SET = 0, FnV = 0
[  191.069004]   EA = 0, S1PTW = 0
[  191.072132] Data abort info:
[  191.074999]   ISV = 0, ISS = 0x00000004
[  191.078822]   CM = 0, WnR = 0
[  191.081780] user pgtable: 4k pages, 48-bit VAs, pgdp = 0000000043d9e467
[  191.088382] [0000000000000000] pgd=0000000000000000
[  191.093252] Internal error: Oops: 96000004 [#1] SMP
[  191.098119] Modules linked in: vhost_net vhost tap vfio_pci vfio_virqfd vfio_iommu_type1 vfio xt_CHECKSUM iptable_mangle ipt_MASQUERADE iptable_nat nf_nat_ipv4 nf_nat xt_conntrack nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge stp llc ebtable_filter devlink ebtables ip6table_filter ip6_tables iptable_filter bpfilter ipmi_ssif nls_iso8859_1 input_leds joydev ipmi_si hns_roce_hw_v2 ipmi_devintf hns_roce ipmi_msghandler cppc_cpufreq sch_fq_codel ib_iser rdma_cm iw_cm ib_cm ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ip_tables x_tables autofs4 ses enclosure btrfs zstd_compress raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor hid_generic usbhid hid raid6_pq libcrc32c raid1 raid0 multipath linear ixgbevf hibmc_drm ttm
[  191.168607]  drm_kms_helper aes_ce_blk aes_ce_cipher syscopyarea crct10dif_ce sysfillrect ghash_ce qla2xxx sysimgblt sha2_ce sha256_arm64 hisi_sas_v3_hw fb_sys_fops sha1_ce uas nvme_fc mpt3sas ixgbe drm hisi_sas_main nvme_fabrics usb_storage hclge scsi_transport_fc ahci libsas hnae3 raid_class libahci xfrm_algo scsi_transport_sas mdio aes_neon_bs aes_neon_blk crypto_simd cryptd aes_arm64
[  191.202952] CPU: 94 PID: 0 Comm: swapper/94 Not tainted 4.19.0-rc1+ #11
[  191.209553] Hardware name: Huawei D06 /D06, BIOS Hisilicon D06 UEFI RC0 - V1.20.01 04/26/2019
[  191.218064] pstate: 20400089 (nzCv daIf +PAN -UAO)
[  191.222873] pc : ixgbe_ipsec_vf_clear+0x60/0xd0 [ixgbe]
[  191.228093] lr : ixgbe_msg_task+0x2d0/0x1088 [ixgbe]
[  191.233044] sp : ffff000009b3bcd0
[  191.236346] x29: ffff000009b3bcd0 x28: 0000000000000000
[  191.241647] x27: ffff000009628000 x26: 0000000000000000
[  191.246946] x25: ffff803f652d7600 x24: 0000000000000004
[  191.252246] x23: ffff803f6a718900 x22: 0000000000000000
[  191.257546] x21: 0000000000000000 x20: 0000000000000000
[  191.262845] x19: 0000000000000000 x18: 0000000000000000
[  191.268144] x17: 0000000000000000 x16: 0000000000000000
[  191.273443] x15: 0000000000000000 x14: 0000000100000026
[  191.278742] x13: 0000000100000025 x12: ffff8a5f7fbe0df0
[  191.284042] x11: 000000010000000b x10: 0000000000000040
[  191.289341] x9 : 0000000000001100 x8 : ffff803f6a824fd8
[  191.294640] x7 : ffff803f6a825098 x6 : 0000000000000001
[  191.299939] x5 : ffff000000f0ffc0 x4 : 0000000000000000
[  191.305238] x3 : ffff000028c00000 x2 : ffff803f652d7600
[  191.310538] x1 : 0000000000000000 x0 : ffff000000f205f0
[  191.315838] Process swapper/94 (pid: 0, stack limit = 0x00000000addfed5a)
[  191.322613] Call trace:
[  191.325055]  ixgbe_ipsec_vf_clear+0x60/0xd0 [ixgbe]
[  191.329927]  ixgbe_msg_task+0x2d0/0x1088 [ixgbe]
[  191.334536]  ixgbe_msix_other+0x274/0x330 [ixgbe]
[  191.339233]  __handle_irq_event_percpu+0x78/0x270
[  191.343924]  handle_irq_event_percpu+0x40/0x98
[  191.348355]  handle_irq_event+0x50/0xa8
[  191.352180]  handle_fasteoi_irq+0xbc/0x148
[  191.356263]  generic_handle_irq+0x34/0x50
[  191.360259]  __handle_domain_irq+0x68/0xc0
[  191.364343]  gic_handle_irq+0x84/0x180
[  191.368079]  el1_irq+0xe8/0x180
[  191.371208]  arch_cpu_idle+0x30/0x1a8
[  191.374860]  do_idle+0x1dc/0x2a0
[  191.378077]  cpu_startup_entry+0x2c/0x30
[  191.381988]  secondary_start_kernel+0x150/0x1e0
[  191.386506] Code: 6b15003f 54000320 f1404a9f 54000060 (79400260)

Fixes: eda0333a ("ixgbe: add VF IPsec management")
Signed-off-by: Dann Frazier <dann.frazier@canonical.com>
Acked-by: Shannon Nelson <snelson@pensando.io>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe_ipsec.c

@@ -842,6 +842,9 @@ void ixgbe_ipsec_vf_clear(struct ixgbe_adapter *adapter, u32 vf)
 	struct ixgbe_ipsec *ipsec = adapter->ipsec;
 	int i;
 
+	if (!ipsec)
+		return;
+
 	/* search rx sa table */
 	for (i = 0; i < IXGBE_IPSEC_MAX_SA_COUNT && ipsec->num_rx_sa; i++) {
 		if (!ipsec->rx_tbl[i].used)