System panic while executing log_entry_set_key function in dsa_filter module codepath

Issue

• Kernel panic due to a NULL pointer dereference in the dsa_filter kernel module.

• Log holds a stack trace similar to the following:

[2522678.952814] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
[2522678.952883] IP: [<ffffffffc0a5f9fa>] log_entry_set_key+0xa/0x340 [dsa_filter]
[2522678.952956] PGD 800000011578a067 PUD 11500b067 PMD 0 
[2522678.953002] Oops: 0000 [#1] SMP 
[2522678.953032] Modules linked in: tcp_diag udp_diag inet_diag falcon_lsm_serviceable(PE) falcon_nf_netcontain(PE) falcon_kal(E) falcon_lsm_pinned_11711(E) gsch(OE) redirfs(OE) acdc(POE) dsa_filter(POE) falcon_lsm_pinned_11611(E) rpcsec_gss_krb5 nfsv4 dns_resolver nfs lockd grace fscache falcon_lsm_pinned_11312(E) vmw_vsock_vmci_transport vsock sb_edac iosf_mbi kvm_intel kvm irqbypass crc32_pclmul ppdev ghash_clmulni_intel vmw_balloon aesni_intel lrw gf128mul glue_helper ablk_helper cryptd pcspkr joydev sg vmw_vmci parport_pc parport i2c_piix4 auth_rpcgss sunrpc ip_tables xfs libcrc32c sr_mod cdrom ata_generic pata_acpi vmwgfx sd_mod crc_t10dif drm_kms_helper crct10dif_generic ata_piix syscopyarea sysfillrect sysimgblt fb_sys_fops ttm libata crct10dif_pclmul crct10dif_common crc32c_intel drm serio_raw
[2522678.953751]  nfit vmxnet3 libnvdimm vmw_pvscsi drm_panel_orientation_quirks dm_mirror dm_region_hash dm_log dm_mod fuse [last unloaded: falcon_kal]
[2522678.953884] CPU: 2 PID: 11985 Comm: dsp.fwdpi.servi Kdump: loaded Tainted: P           OEL ------------   3.10.0-1160.24.1.el7.x86_64 #1
[2522678.953966] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 12/12/2018
[2522678.954039] task: ffff9e1ab7ff2100 ti: ffff9e1a46d44000 task.ti: ffff9e1a46d44000
[2522678.954091] RIP: 0010:[<ffffffffc0a5f9fa>]  [<ffffffffc0a5f9fa>] log_entry_set_key+0xa/0x340 [dsa_filter]
[2522678.954187] RSP: 0018:ffff9e1a46d474e0  EFLAGS: 00010246
[2522678.954237] RAX: 0000000000000000 RBX: ffff9e1a46d47db0 RCX: 0000000000010000
[2522678.954287] RDX: ffff9e1a46d47db0 RSI: 000000000000001d RDI: ffff9e1a46d47db0
[2522678.954337] RBP: ffff9e1a46d474e8 R08: 0000000000010000 R09: ffff9e1a46d47eac
[2522678.954396] R10: 00000000c8d5c401 R11: ffff9e1bc8d5c330 R12: ffff9e19fae86de0
[2522678.954496] R13: ffff9e1a46d47eac R14: 0000000000000008 R15: 000000000000001d
[2522678.954548] FS:  00007f9b9673c700(0000) GS:ffff9e1d7fd00000(0000) knlGS:0000000000000000
[2522678.954604] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[2522678.954645] CR2: 0000000000000020 CR3: 00000002b1978000 CR4: 00000000003607e0
[2522678.954771] Call Trace:
[2522678.954807]  [<ffffffffc0a5fef7>] get_logs_from_tree+0xf7/0x2e0 [dsa_filter]
[2522678.954865]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.954922]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.954978]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.955035]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.955091]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.955148]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.955204]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.955260]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.957014]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.958520]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.959328]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.960144]  [<ffffffff878bb8b1>] ? iomap_file_buffered_write+0xa1/0xe0
[2522678.960959]  [<ffffffffc05b13c4>] ? xfs_iunlock+0xe4/0x120 [xfs]
[2522678.961746]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.962545]  [<ffffffffc08db55f>] ? redirfs_get_filename+0x4ff/0x520 [redirfs]
[2522678.963358]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.964164]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.964962]  [<ffffffff876e12ae>] ? account_entity_dequeue+0xae/0xd0
[2522678.965769]  [<ffffffff876e61d1>] ? put_prev_entity+0x31/0x400
[2522678.966586]  [<ffffffffc0a5fea4>] get_logs_from_tree+0xa4/0x2e0 [dsa_filter]
[2522678.967391]  [<ffffffff8762b621>] ? __switch_to+0x151/0x580
[2522678.968225]  [<ffffffffc0a62fcc>] tb_log_get+0x75c/0x930 [dsa_filter]
[2522678.969031]  [<ffffffffc0abdf73>] dsa_lin_read+0x53/0xd0 [dsa_filter]
[2522678.969813]  [<ffffffff8784dc6f>] vfs_read+0x9f/0x170
[2522678.970584]  [<ffffffff8784eaef>] SyS_read+0x7f/0xf0
[2522678.971382]  [<ffffffff87d95f92>] system_call_fastpath+0x25/0x2a
[2522678.972142] Code: 00 e8 8b 6e 00 00 e8 66 36 06 00 48 c7 c0 80 17 ae c0 5d c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 e8 6b a0 33 c7 55 48 89 e5 53 <80> 7e 03 11 48 89 f3 0f 87 99 02 00 00 0f b6 46 03 48 8b 04 c5 
[2522678.973784] RIP  [<ffffffffc0a5f9fa>] log_entry_set_key+0xa/0x340 [dsa_filter]
[2522678.974570]  RSP <ffff9e1a46d474e0>
[2522678.975294] CR2: 0000000000000020