kernel crashed at `tty_devnum()` using 3rd party module `RedCastle` in Red Hat Enterprise Linux.

Issue

• kernel crashed with following log:

<1>BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
<1>IP: [<ffffffff8132f249>] tty_devnum+0x9/0x30
<4>Oops: 0000 [#1] SMP
<4>Modules linked in: symbdsnap(P)(U) des_generic ecb md4 nls_utf8 cifs RedCastle(P)(U) mptctl mptbase cpufreq_ondemand freq_table pcc_cpufreq bonding 8021q garp stp llc ipv6 vhost_net macvtap macvlan tun kvm_intel kvm uinput iTCO_wdt iTCO_vendor_support microcode serio_raw sb_edac edac_core power_meter acpi_ipmi ipmi_si ipmi_msghandler i2c_i801 i2c_core lpc_ich mfd_core tg3 hpilo hpwdt sg ixgbe dca ptp pps_core mdio ext4 jbd2 mbcache usb_storage sr_mod cdrom sd_mod crc_t10dif ahci xhci_hcd hpsa wmi dm_mirror dm_region_hash dm_log dm_mod [last unloaded: scsi_wait_scan]
<4>
<4>Pid: 11258, comm: bash Tainted: P           ---------------    2.6.32-504.el6.x86_64 #1 HP ProLiant DL380 Gen9/ProLiant DL380 Gen9
<4>RIP: 0010:[<ffffffff8132f249>]  [<ffffffff8132f249>] tty_devnum+0x9/0x30
<4>RSP: 0018:ffff88044f4e9a88  EFLAGS: 00010286
<4>RAX: 00000000ffffffff RBX: ffff88044f4e9d58 RCX: 0000000001b6f190
<4>RDX: ffff880f27262500 RSI: 0000000000000003 RDI: 0000000000000000
<4>RBP: ffff88044f4e9a88 R08: ffff881031f554e8 R09: 0000000000000000
<4>R10: 0000000000000000 R11: 0000000000000246 R12: ffff881031f554e8
<4>R13: 0000000000000003 R14: ffff881031f554e8 R15: 0000000000000003
<4>FS:  00007f171a02f700(0000) GS:ffff880028200000(0000) knlGS:0000000000000000
<4>CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4>CR2: 0000000000000008 CR3: 0000000da0862000 CR4: 00000000001407f0
<4>DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
<4>DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
<4>Process bash (pid: 11258, threadinfo ffff88044f4e8000, task ffff880e3d580040)
<4>Stack:
<4> ffff88044f4e9a98 ffffffffa039e014 ffff88044f4e9ba8 ffffffffa0382f5d
<4><d> ffff88044f4e9ac8 ffffffff8119c731 0000000000000000 0000000000000001
<4><d> ffff88044f4e9ba8 ffffffffa038e95c ffff8810620d9ec0 0000000001b6f190
<4>Call Trace:
<4> [<ffffffffa039e014>] get_tty_linux+0x34/0x40 [RedCastle]
<4> [<ffffffffa0382f5d>] check_file_acl+0x18d/0xbf0 [RedCastle]
<4> [<ffffffff8119c731>] ? path_put+0x31/0x40
<4> [<ffffffffa038e95c>] ? wr_lookupname+0x9c/0xe0 [RedCastle]
<4> [<ffffffffa039485a>] rg_lookuppn_acl+0x2da/0x570 [RedCastle]
<4> [<ffffffff8119c731>] ? path_put+0x31/0x40
<4> [<ffffffff8119f5d1>] ? filename_lookup+0x41/0xc0
<4> [<ffffffff8119bb76>] ? final_putname+0x26/0x50
<4> [<ffffffff8119c17b>] ? putname+0x2b/0x40
<4> [<ffffffffa038e968>] ? wr_lookupname+0xa8/0xe0 [RedCastle]
<4> [<ffffffffa039e14c>] ? copyinstr+0x4c/0x80 [RedCastle]
<4> [<ffffffffa0394f21>] rg_lookupname_acl+0x111/0x1d0 [RedCastle]
<4> [<ffffffffa039c135>] ? ips_open_pre+0x145/0x2e0 [RedCastle]
<4> [<ffffffffa038953d>] ac_preproc+0x6d/0x1c0 [RedCastle]
<4> [<ffffffff8152c166>] ? down_read+0x16/0x30
<4> [<ffffffffa039c508>] prst_open+0x238/0x370 [RedCastle]
<4> [<ffffffffa039c6af>] rg_open+0x6f/0xe0 [RedCastle]
<4> [<ffffffff8152d375>] ? page_fault+0x25/0x30
<4> [<ffffffff8100b072>] system_call_fastpath+0x16/0x1b
<4>Code: 66 90 55 48 89 e5 0f 1f 44 00 00 48 89 b7 00 01 00 00 c9 c3 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 0f 1f 44 00 00 <48> 8b 57 08 8b 82 8c 00 00 00 c1 e0 14 0b 82 90 00 00 00 03 47
<1>RIP  [<ffffffff8132f249>] tty_devnum+0x9/0x30
<4> RSP <ffff88044f4e9a88>
<4>CR2: 0000000000000008