net/mxl5e: Verify that rpriv is not NULL

net/mxl5e: Verify that rpriv is not NULL

In helper function is_flow_rule_duplicate_allowed() verify that rpviv
pointer is not NULL before dereferencing it. This can happen when device is
in NIC mode and leads to following crash:

[90444.046419] BUG: kernel NULL pointer dereference, address: 0000000000000000
[90444.048149] #PF: supervisor read access in kernel mode
[90444.049781] #PF: error_code(0x0000) - not-present page
[90444.051386] PGD 80000003d35a4067 P4D 80000003d35a4067 PUD 3d35a3067 PMD 0
[90444.053051] Oops: 0000 [#1] SMP PTI
[90444.054683] CPU: 16 PID: 31736 Comm: tc Not tainted 5.8.0-rc1+ #1157
[90444.056340] Hardware name: Supermicro SYS-2028TP-DECR/X10DRT-P, BIOS 2.0b 03/30/2017
[90444.058079] RIP: 0010:mlx5e_configure_flower+0x3aa/0x9b0 [mlx5_core]
[90444.059753] Code: 24 50 49 8b 95 08 02 00 00 48 b8 00 08 00 00 04 00 00 00 48 21 c2 48 39 c2 74 0a 41 f6 85 0d 02 00 00 20 74 16 48 8b 44 24 20 <48> 8b 00 66 83 78 20 ff 74 07 4d 89 aa e0 00 00 00 48 83 7d 28 00
[90444.063232] RSP: 0018:ffffabe9c61ff768 EFLAGS: 00010246
[90444.065014] RAX: 0000000000000000 RBX: ffff9b13c4c91e80 RCX: 00000000000093fa
[90444.066784] RDX: 0000000400000800 RSI: 0000000000000000 RDI: 000000000002d5e0
[90444.068533] RBP: ffff9b174d308468 R08: 0000000000000000 R09: ffff9b17d63003f0
[90444.070285] R10: ffff9b17ea288600 R11: 0000000000000000 R12: ffffabe9c61ff878
[90444.072032] R13: ffff9b174d300000 R14: ffffabe9c61ffbb8 R15: ffff9b174d300880
[90444.073760] FS:  00007f3c23775480(0000) GS:ffff9b13efc80000(0000) knlGS:0000000000000000
[90444.075492] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[90444.077266] CR2: 0000000000000000 CR3: 00000003e2a60002 CR4: 00000000001606e0
[90444.079024] Call Trace:
[90444.080753]  tc_setup_cb_add+0xca/0x1e0
[90444.082415]  fl_hw_replace_filter+0x15f/0x1f0 [cls_flower]
[90444.084119]  fl_change+0xa59/0x13dc [cls_flower]
[90444.085772]  ? wait_for_completion+0xa8/0xf0
[90444.087364]  tc_new_tfilter+0x3f5/0xa60
[90444.088960]  rtnetlink_rcv_msg+0xeb/0x360
[90444.090514]  ? __d_lookup_done+0x76/0xe0
[90444.092034]  ? proc_alloc_inode+0x16/0x70
[90444.093560]  ? prep_new_page+0x8c/0xf0
[90444.095048]  ? _cond_resched+0x15/0x30
[90444.096483]  ? rtnl_calcit.isra.0+0x110/0x110
[90444.097907]  netlink_rcv_skb+0x49/0x110
[90444.099289]  netlink_unicast+0x191/0x230
[90444.100629]  netlink_sendmsg+0x243/0x480
[90444.101984]  sock_sendmsg+0x5e/0x60
[90444.103305]  ____sys_sendmsg+0x1f3/0x260
[90444.104597]  ? copy_msghdr_from_user+0x5c/0x90
[90444.105916]  ? __mod_lruvec_state+0x3c/0xe0
[90444.107210]  ___sys_sendmsg+0x81/0xc0
[90444.108484]  ? do_filp_open+0xa5/0x100
[90444.109732]  ? handle_mm_fault+0x117b/0x1e00
[90444.110970]  ? __check_object_size+0x46/0x147
[90444.112205]  ? __check_object_size+0x136/0x147
[90444.113402]  __sys_sendmsg+0x59/0xa0
[90444.114587]  do_syscall_64+0x4d/0x90
[90444.115782]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[90444.116953] RIP: 0033:0x7f3c2393b7b8
[90444.118101] Code: Bad RIP value.
[90444.119240] RSP: 002b:00007ffc6ad8e6c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
[90444.120408] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f3c2393b7b8
[90444.121583] RDX: 0000000000000000 RSI: 00007ffc6ad8e740 RDI: 0000000000000003
[90444.122750] RBP: 000000005eea0c3a R08: 0000000000000001 R09: 00007ffc6ad8e68c
[90444.123928] R10: 0000000000404fa8 R11: 0000000000000246 R12: 0000000000000001
[90444.125073] R13: 0000000000000000 R14: 00007ffc6ad92a00 R15: 00000000004866a0
[90444.126221] Modules linked in: act_skbedit act_tunnel_key act_mirred bonding vxlan ip6_udp_tunnel udp_tunnel nfnetlink act_gact cls_flower sch_ingress openvswitch nsh nf_conncount nfsv3 nfs_acl nfs lockd grace fscache tun bridge stp llc sunrpc rdma_ucm rdma_cm iw_cm ib_cm mlx5_ib ib_uverbs ib_core mlx5_core intel_r
apl_msr intel_rapl_common sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel mlxfw kvm act_ct nf_flow_table nf_nat nf_conntrack irqbypass crct10dif_pclmul nf_defrag_ipv6 igb ipmi_ssif libcrc32c crc32_pclmul crc32c_intel ipmi_si nf_defrag_ipv4 ptp ghash_clmulni_intel mei_me ses iTCO_wdt i2c_i801 pps_core
ioatdma iTCO_vendor_support joydev mei enclosure intel_cstate i2c_smbus wmi dca ipmi_devintf intel_uncore lpc_ich ipmi_msghandler pcspkr acpi_pad acpi_power_meter ast i2c_algo_bit drm_vram_helper drm_kms_helper drm_ttm_helper ttm drm mpt3sas raid_class scsi_transport_sas
[90444.136253] CR2: 0000000000000000
[90444.137621] ---[ end trace 924af62aa2b151bd ]---

Fixes: 553f9328385d ("net/mlx5e: Support tc block sharing for representors")
Reported-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>