2

I'm trying to see the content of the /proc/iomem. Upon running both

$ cat /proc/iomem
$ cat sudo /proc/iomem

I'm getting the same message killed in the terminal. And the dmesg shows the following,

[  432.902434] Call Trace:
[  432.902438]  [<ffffffff81244e00>] seq_read+0x300/0x3d0
[  432.902441]  [<ffffffff8128d775>] proc_reg_read+0x45/0x70
[  432.902443]  [<ffffffff8121e76b>] __vfs_read+0x1b/0x40
[  432.902445]  [<ffffffff8121eee6>] vfs_read+0x86/0x130
[  432.902446]  [<ffffffff8121fc3c>] SyS_read+0x5c/0xe0
[  432.902449]  [<ffffffff8186ac9b>] entry_SYSCALL_64_fastpath+0x22/0xd0
[  432.902450] Code: 41 55 41 54 53 49 89 fd 49 89 f6 48 83 ec 18 48 8b 8f 80 00 00 00 48 81 79 08 00 00 01 00 45 19 e4 31 d2 41 83 e4 fc 41 83 c4 08 <48> 8b 40 20 48 39 c1 74 7e 83 c2 01 83 fa 05 75 ef bb 0a 00 00 
[  432.902469] RIP  [<ffffffff8108be09>] r_show+0x39/0xd0
[  432.902471]  RSP <ffff88047a0b3df0>
[  432.902471] CR2: 0000000000000020
[  432.902473] ---[ end trace 6dbfc91babedf8d6 ]---

More info : as suggested journalctl -xe shows the following

Mar 02 16:15:06 sourav kernel: ---[ end trace 6dbfc91babedf8d8 ]---
Mar 02 16:17:01 sourav CRON[9604]: pam_unix(cron:session): session opened for user root by (uid=0)
Mar 02 16:17:01 sourav CRON[9605]: (root) CMD (   cd / && run-parts --report /etc/cron.hourly)
Mar 02 16:17:01 sourav CRON[9604]: pam_unix(cron:session): session closed for user root
Mar 02 16:22:15 sourav wpa_supplicant[1556]: wlp61s0: SME: Trying to authenticate with 00:c8:8b:e8:76:ce (SSID='eduroam' freq=5280 MHz)
Mar 02 16:22:15 sourav kernel: wlp61s0: authenticate with 00:c8:8b:e8:76:ce
Mar 02 16:22:16 sourav kernel: wlp61s0: send auth to 00:c8:8b:e8:76:ce (try 1/3)
Mar 02 16:22:16 sourav wpa_supplicant[1556]: wlp61s0: Trying to associate with 00:c8:8b:e8:76:ce (SSID='eduroam' freq=5280 MHz)
Mar 02 16:22:16 sourav kernel: wlp61s0: authenticated
Mar 02 16:22:16 sourav kernel: wlp61s0: associate with 00:c8:8b:e8:76:ce (try 1/3)
Mar 02 16:22:16 sourav kernel: wlp61s0: RX AssocResp from 00:c8:8b:e8:76:ce (capab=0x111 status=0 aid=13)
Mar 02 16:22:16 sourav kernel: wlp61s0: associated
Mar 02 16:22:16 sourav wpa_supplicant[1556]: wlp61s0: Associated with 00:c8:8b:e8:76:ce
Mar 02 16:22:16 sourav kernel: cfg80211: World regulatory domain updated:
Mar 02 16:22:16 sourav kernel: cfg80211:  DFS Master region: unset
Mar 02 16:22:16 sourav kernel: cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp), (dfs_cac_time)
Mar 02 16:22:16 sourav kernel: cfg80211:   (2402000 KHz - 2472000 KHz @ 40000 KHz), (N/A, 2000 mBm), (N/A)
Mar 02 16:22:16 sourav kernel: cfg80211:   (2457000 KHz - 2482000 KHz @ 20000 KHz, 92000 KHz AUTO), (N/A, 2000 mBm), (N/A)
Mar 02 16:22:16 sourav kernel: cfg80211:   (2474000 KHz - 2494000 KHz @ 20000 KHz), (N/A, 2000 mBm), (N/A)
Mar 02 16:22:16 sourav kernel: cfg80211:   (5170000 KHz - 5250000 KHz @ 80000 KHz, 160000 KHz AUTO), (N/A, 2000 mBm), (N/A)
Mar 02 16:22:16 sourav kernel: cfg80211:   (5250000 KHz - 5330000 KHz @ 80000 KHz, 160000 KHz AUTO), (N/A, 2000 mBm), (0 s)
Mar 02 16:22:16 sourav kernel: cfg80211:   (5490000 KHz - 5730000 KHz @ 160000 KHz), (N/A, 2000 mBm), (0 s)
Mar 02 16:22:16 sourav kernel: cfg80211:   (5735000 KHz - 5835000 KHz @ 80000 KHz), (N/A, 2000 mBm), (N/A)
Mar 02 16:22:16 sourav kernel: cfg80211:   (57240000 KHz - 63720000 KHz @ 2160000 KHz), (N/A, 0 mBm), (N/A)
Mar 02 16:22:16 sourav wpa_supplicant[1556]: p2p-dev-wlp61s0: CTRL-EVENT-REGDOM-CHANGE init=CORE type=WORLD
Mar 02 16:22:16 sourav wpa_supplicant[1556]: wlp61s0: WPA: Key negotiation completed with 00:c8:8b:e8:76:ce [PTK=CCMP GTK=CCMP]
Mar 02 16:22:16 sourav wpa_supplicant[1556]: wlp61s0: CTRL-EVENT-CONNECTED - Connection to 00:c8:8b:e8:76:ce completed [id=0 id_str=]
Mar 02 16:22:16 sourav wpa_supplicant[1556]: p2p-dev-wlp61s0: CTRL-EVENT-REGDOM-CHANGE init=COUNTRY_IE type=COUNTRY alpha2=US
Mar 02 16:22:16 sourav kernel: ath: EEPROM regdomain: 0x8348
Mar 02 16:22:16 sourav kernel: ath: EEPROM indicates we should expect a country code
Mar 02 16:22:16 sourav kernel: ath: doing EEPROM country->regdmn map search
Mar 02 16:22:16 sourav kernel: ath: country maps to regdmn code: 0x3a
Mar 02 16:22:16 sourav kernel: ath: Country alpha2 being used: US
Mar 02 16:22:16 sourav kernel: ath: Regpair used: 0x3a
Mar 02 16:22:16 sourav kernel: ath: regdomain 0x8348 dynamically updated by country IE
Mar 02 16:22:16 sourav kernel: cfg80211: Regulatory domain changed to country: US
Mar 02 16:22:16 sourav kernel: cfg80211:  DFS Master region: FCC
Mar 02 16:22:16 sourav kernel: cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp), (dfs_cac_time)
Mar 02 16:22:16 sourav kernel: cfg80211:   (2400000 KHz - 2472000 KHz @ 40000 KHz), (N/A, 3000 mBm), (N/A)
Mar 02 16:22:16 sourav kernel: cfg80211:   (5150000 KHz - 5250000 KHz @ 80000 KHz, 200000 KHz AUTO), (N/A, 2300 mBm), (N/A)
Mar 02 16:22:16 sourav kernel: cfg80211:   (5250000 KHz - 5350000 KHz @ 80000 KHz, 200000 KHz AUTO), (N/A, 2300 mBm), (0 s)
Mar 02 16:22:16 sourav kernel: cfg80211:   (5470000 KHz - 5730000 KHz @ 160000 KHz), (N/A, 2300 mBm), (0 s)
Mar 02 16:22:16 sourav kernel: cfg80211:   (5730000 KHz - 5850000 KHz @ 80000 KHz), (N/A, 3000 mBm), (N/A)
Mar 02 16:22:16 sourav kernel: cfg80211:   (57240000 KHz - 71000000 KHz @ 2160000 KHz), (N/A, 4000 mBm), (N/A)
Mar 02 16:22:16 sourav kernel: wlp61s0: Limiting TX power to 14 dBm as advertised by 00:c8:8b:e8:76:ce
Mar 02 16:22:16 sourav wpa_supplicant[1556]: wlp61s0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-47 noise=-100 txrate=6000
Mar 02 16:23:07 sourav wpa_supplicant[1556]: wlp61s0: WPA: Group rekeying completed with 00:c8:8b:e8:76:ce [GTK=CCMP]
Mar 02 16:29:13 sourav kernel: BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
Mar 02 16:29:13 sourav kernel: IP: [<ffffffff8108be09>] r_show+0x39/0xd0
Mar 02 16:29:13 sourav kernel: PGD 80000003c33af067 PUD 3c33ae067 PMD 0 
Mar 02 16:29:13 sourav kernel: Oops: 0000 [#6] SMP 
Mar 02 16:29:13 sourav kernel: Modules linked in: iptable_filter ip_tables x_tables drbg ansi_cprng ctr ccm rfcomm arc4 bnep snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic intel_rapl x86_p
Mar 02 16:29:13 sourav kernel:  int3403_thermal int340x_thermal_zone intel_hid int3400_thermal sparse_keymap acpi_thermal_rel mac_hid acpi_pad parport_pc ppdev lp parport autofs4 hid_generic usbhid hid no
Mar 02 16:29:13 sourav kernel: CPU: 5 PID: 10396 Comm: cat Tainted: P      D    OE   4.4.0-200-generic #232-Ubuntu
Mar 02 16:29:13 sourav kernel: Hardware name: Alienware Alienware 15 R3/Alienware 15 R3, BIOS 1.8.0 05/28/2019
Mar 02 16:29:13 sourav kernel: task: ffff880058fe1e80 ti: ffff8803b4128000 task.ti: ffff8803b4128000
Mar 02 16:29:13 sourav kernel: RIP: 0010:[<ffffffff8108be09>]  [<ffffffff8108be09>] r_show+0x39/0xd0
Mar 02 16:29:13 sourav kernel: RSP: 0018:ffff8803b412bdf0  EFLAGS: 00010297
Mar 02 16:29:13 sourav kernel: RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81e43f60
Mar 02 16:29:13 sourav kernel: RDX: 0000000000000001 RSI: ffff88047845e4a8 RDI: ffff88047b5713c0
Mar 02 16:29:13 sourav kernel: RBP: ffff8803b412be28 R08: 0000000000001000 R09: 00000000000005a5
Mar 02 16:29:13 sourav kernel: R10: ffff88047b124000 R11: ffff88047b124595 R12: 0000000000000008
Mar 02 16:29:13 sourav kernel: R13: ffff88047b5713c0 R14: ffff88047845e4a8 R15: ffff88047845e4a8
Mar 02 16:29:13 sourav kernel: FS:  00007f3578c13700(0000) GS:ffff880491d40000(0000) knlGS:0000000000000000
Mar 02 16:29:13 sourav kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Mar 02 16:29:13 sourav kernel: CR2: 0000000000000020 CR3: 0000000410c86000 CR4: 0000000000360670
Mar 02 16:29:13 sourav kernel: Stack:
Mar 02 16:29:13 sourav kernel:  ffff880300000008 0000000000000000 ffffffffc06d1377 0000000000000000
Mar 02 16:29:13 sourav kernel:  ffff8803b412bf18 ffff880410d2d800 ffff88047b5713c0 ffff8803b412be98
Mar 02 16:29:13 sourav kernel:  ffffffff81244e00 00000000000005a5 00007f3578bf1000 ffff88047b571400
Mar 02 16:29:13 sourav kernel: Call Trace:
Mar 02 16:29:13 sourav kernel:  [<ffffffff81244e00>] seq_read+0x300/0x3d0
Mar 02 16:29:13 sourav kernel:  [<ffffffff8128d775>] proc_reg_read+0x45/0x70
Mar 02 16:29:13 sourav kernel:  [<ffffffff8121e76b>] __vfs_read+0x1b/0x40
Mar 02 16:29:13 sourav kernel:  [<ffffffff8121eee6>] vfs_read+0x86/0x130
Mar 02 16:29:13 sourav kernel:  [<ffffffff8121fc3c>] SyS_read+0x5c/0xe0
Mar 02 16:29:13 sourav kernel:  [<ffffffff8186ac9b>] entry_SYSCALL_64_fastpath+0x22/0xd0
Mar 02 16:29:13 sourav kernel: Code: 41 55 41 54 53 49 89 fd 49 89 f6 48 83 ec 18 48 8b 8f 80 00 00 00 48 81 79 08 00 00 01 00 45 19 e4 31 d2 41 83 e4 fc 41 83 c4 08 <48> 8b 40 20 48 39 c1 74 7e 83 c2 01 
Mar 02 16:29:13 sourav kernel: RIP  [<ffffffff8108be09>] r_show+0x39/0xd0
Mar 02 16:29:13 sourav kernel:  RSP <ffff8803b412bdf0>
Mar 02 16:29:13 sourav kernel: CR2: 0000000000000020
Mar 02 16:29:13 sourav kernel: ---[ end trace 6dbfc91babedf8d9 ]---

I tried to restart the system but it just stalls. I force restart the system but the problem persists. Any help how to fix this?

3
  • Can we assume you intended to write sudo cat /proc/iomem (in place of cat sudo /proc/iomem)? – steeldriver Mar 3 at 0:14
  • 1
    This looks like a kernel bug, similar to the one discussed here BUG: unable to handle kernel NULL pointer dereference. I don't have any suggestions for debugging, except to note that based on the Tainted: P D OE 4.4.0-200-generic string, it looks like the kernel includes one or more proprietary/unsigned/out-of-tree modules - see Tainted kernels – steeldriver Mar 3 at 0:30
  • 1
    I was thinking along the lines of what @steeldriver said. I also noticed cat in the same line he quoted which is what lead me to suggest head or tail instead of cat. Also you can try dmesg | grep -i taint. Something else I read but don't fully understand yet is cat /proc/sys/kernel/tainted or head if cat fails. – WinEunuuchs2Unix Mar 3 at 1:53

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