Re: BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 in nilfs_segctor_do_construct

[ARAI Shun-ichi]

Hi,

It is reproducible in my environment.
Kernel version is 4.19.86 (Gentoo).
NILFS2 with kernel 4.19.82 works well.

I did following for the test.

i) mount corrupt partition with read-only option
 (this partition causes "mounting fs with errors" at every rw mount)
 i-1) wait a few minutes ... not crash
 i-2) fs access (ls, du, ...) ... not crash

ii) create small NILFS2 fs and read-write mount
 dd if=/dev/zero of=/tmp/n bs=1M count=500
 mount -o loop /tmp/n /mnt/tmp
 ii-1) wait a few minutes ... not crash
 ii-2) touch file in the fs ... crash (in few seconds)


In <CAKFNMo=k1wVHOwXhTLEOJ+A-nwmvJ+sN_PPa8kY8fMxrQ4R+Jw@xxxxxxxxxxxxxx>;
   Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> wrote
   as Subject "Re: BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 in nilfs_segctor_do_construct":

> Hi,
> 
>> It was likely caused by improper shutdown and following nilfs2 partition
>> corruption.  Now I can still read the data, but on the whole the
>> computer is not useable, because starting a process which uses the
>> corrupted file system simply crashes in kernel.
> 
> Thank you for reporting the issue.
> Let me ask you a few questions:
> 
> 1) Is the crash reproducible in the environment ?
> 2) Can you mount the corrupted(?) partition from a recent version of kernel ?
> 3) Does read-only mount option (-r) work to avoid the crash ?
> 
> Thanks,
> Ryusuke Konishi
> 
> 2019年11月18日(月) 2:34 Tomas Hlavaty <tom@xxxxxxxxxx>:
>>
>> Hi Ryusuke,
>>
>> today I got this bug in kernel, which seems to be related to nilfs2.
>>
>> It was likely caused by improper shutdown and following nilfs2 partition
>> corruption.  Now I can still read the data, but on the whole the
>> computer is not useable, because starting a process which uses the
>> corrupted file system simply crashes in kernel.  I am actually not sure
>> if the filesystem is corrupted, as I don't know about any tool to check
>> that.  The relevant parts of dmesg log are bellow.
>>
>> Please let me know if you are the right contact or if you need more info
>> about the problem.
>>
>> Thank you,
>>
>> Tomas
>>
>> [    0.000000] Linux version 4.19.84 (nixbld@localhost) (gcc version 8.3.0 (GCC)) #1-NixOS SMP Tue Nov 12 18:21:46 UTC 2019
>> [    0.000000] Command line: initrd=\efi\nixos\4s51zw36kd1qb0ymk0charxjg8x6k5k3-initrd-linux-4.19.84-initrd.efi systemConfig=/nix/store/gdbxhzysr929abrymjqala0b5bh2fqmv-nixos-system-ushi-19.09.1258.07e66484e67 init=/nix/store/gdbxhzysr929abrymjqala0b5bh2fqmv-nixos-system-ushi-19.09.1258.07e66484e67/init loglevel=4
>>
>>
>>
>> [   37.741106] systemd-journald[470]: Received client request to flush runtime journal.
>> [   37.749084] systemd-journald[470]: File /var/log/journal/55a4ea9159c14c0bb8767a43819c6927/system.journal corrupted or uncleanly shut down, renaming and replacing.
>> [   37.810819] audit: type=1130 audit(1573985039.617:3): pid=1 uid=0 auid=4294967295 ses=4294967295 subj==unconfined msg='unit=systemd-udevd comm="systemd" exe="/nix/store/v8flm2h07zcfg5k5npz56m0ayj0qm1q8-systemd-243/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
>>
>> [   38.321561] NILFS version 2 loaded
>> [   38.323236] NILFS (dm-1): mounting unchecked fs
>>
>>
>> [   38.349185] NILFS (dm-1): recovery complete
>> [   38.353228] NILFS (dm-1): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
>>
>> [   63.543941] systemd-journald[470]: File
>> /var/log/journal/55a4ea9159c14c0bb8767a43819c6927/user-1000.journal
>> corrupted or uncleanly shut down, renaming and replacing.
>>
>> [12637.085548] BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8
>> [12637.085558] PGD 0 P4D 0
>> [12637.085567] Oops: 0000 [#1] SMP PTI
>> [12637.085574] CPU: 0 PID: 657 Comm: segctord Not tainted 4.19.84 #1-NixOS
>> [12637.085577] Hardware name: ASUSTeK COMPUTER INC. VivoBook 15_ASUS Laptop X507MA_R507MA/X507MA, BIOS X507MA.301 09/14/2018
>> [12637.085589] RIP: 0010:percpu_counter_add_batch+0x4/0x60
>> [12637.085593] Code: 89 e6 89 c7 e8 dd 3b 28 00 3b 05 fb e0 b6 00 72 d8 4c 89 ee 48 89 ef e8 7a 63 2a 00 48 89 d8 5b 5d 41 5c 41 5d c3 41 54 55 53 <48> 8b 47 20 65 44 8b 20 49 63 ec 48 63 ca 48 01 f5 48 39 e9 7e 0a
>> [12637.085597] RSP: 0018:ffff9d1b00a0bd20 EFLAGS: 00010006
>> [12637.085601] RAX: 0000000000000002 RBX: 0000000000000000 RCX: 0000000000000018
>> [12637.085604] RDX: 0000000000000018 RSI: 0000000000000001 RDI: 0000000000000088
>> [12637.085608] RBP: ffff8df67a2988d0 R08: 0000000000000000 R09: ffff8df66fe0cfe0
>> [12637.085611] R10: 0000000000000230 R11: 0000000000000000 R12: 0000000000000000
>> [12637.085614] R13: ffff8df67a298758 R14: ffff8df67a2988c8 R15: ffffccd684229a80
>> [12637.085618] FS:  0000000000000000(0000) GS:ffff8df67ba00000(0000) knlGS:0000000000000000
>> [12637.085621] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [12637.085624] CR2: 00000000000000a8 CR3: 000000011ac0a000 CR4: 0000000000340ef0
>> [12637.085628] Call Trace:
>> [12637.085640]  __test_set_page_writeback+0x37c/0x3f0
>> [12637.085663]  nilfs_segctor_do_construct+0x184e/0x2040 [nilfs2]
>> [12637.085680]  nilfs_segctor_construct+0x1f5/0x2e0 [nilfs2]
>> [12637.085693]  nilfs_segctor_thread+0x129/0x370 [nilfs2]
>> [12637.085706]  ? nilfs_segctor_construct+0x2e0/0x2e0 [nilfs2]
>> [12637.085713]  kthread+0x112/0x130
>> [12637.085719]  ? kthread_bind+0x30/0x30
>> [12637.085728]  ret_from_fork+0x1f/0x40
>> [12637.085734] Modules linked in: ctr ccm af_packet msr 8021q snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic hid_multitouch arc4 ath9k ath9k_common ath9k_hw ath mac80211 snd_soc_skl snd_soc_skl_ipc spi_pxa2xx_platform asus_nb_wmi snd_soc_sst_ipc snd_soc_sst_dsp asus_wmi 8250_dw i2c_designware_platform sparse_keymap i2c_designware_core wmi_bmof i915 snd_hda_ext_core nilfs2 snd_soc_acpi_intel_match snd_soc_acpi uvcvideo videobuf2_vmalloc nls_iso8859_1 videobuf2_memops videobuf2_v4l2 snd_soc_core nls_cp437 rtsx_usb_ms intel_telemetry_pltdrv vfat intel_punit_ipc intel_telemetry_core fat intel_pmc_ipc memstick videobuf2_common snd_compress kvmgt vfio_mdev mdev ath3k vfio_iommu_type1 vfio btusb ac97_bus snd_pcm_dmaengine btrtl x86_pkg_temp_thermal intel_powerclamp btbcm cec coretemp btintel
>> [12637.085819]  crct10dif_pclmul crc32_pclmul videodev snd_hda_intel bluetooth drm_kms_helper ghash_clmulni_intel deflate media efi_pstore intel_cstate pstore intel_rapl_perf cfg80211 snd_hda_codec joydev mousedev evdev wdat_wdt serio_raw mac_hid efivars drm snd_hda_core snd_hwdep ecdh_generic snd_pcm snd_timer mei_me idma64 virt_dma snd intel_gtt agpgart i2c_i801 i2c_algo_bit mei fb_sys_fops syscopyarea soundcore rfkill processor_thermal_device sysfillrect sysimgblt intel_lpss_pci intel_soc_dts_iosf thermal wmi intel_lpss i2c_hid i2c_core battery tpm_crb button ac tpm_tis tpm_tis_core asus_wireless video pcc_cpufreq tpm rng_core pinctrl_geminilake int3400_thermal int3403_thermal pinctrl_intel int340x_thermal_zone acpi_thermal_rel iptable_nat nf_nat_ipv4 nf_nat xt_conntrack nf_conntrack nf_defrag_ipv6
>> [12637.085912]  nf_defrag_ipv4 libcrc32c ip6t_rpfilter ipt_rpfilter ip6table_raw iptable_raw xt_pkttype nf_log_ipv6 nf_log_ipv4 nf_log_common xt_LOG xt_tcpudp ip6table_filter ip6_tables iptable_filter sch_fq_codel loop cpufreq_powersave tun tap macvlan bridge stp llc kvm_intel kvm irqbypass efivarfs ip_tables x_tables ipv6 crc_ccitt autofs4 ext4 crc32c_generic crc16 mbcache jbd2 fscrypto dm_crypt algif_skcipher af_alg rtsx_usb_sdmmc mmc_core rtsx_usb hid_generic usbhid hid sd_mod input_leds led_class atkbd libps2 ahci libahci xhci_pci libata xhci_hcd aesni_intel usbcore aes_x86_64 crypto_simd scsi_mod cryptd glue_helper crc32c_intel usb_common rtc_cmos i8042 serio dm_mod
>> [12637.086000] CR2: 00000000000000a8
>> [12637.086005] ---[ end trace ee0079180c990cd2 ]---
>> [12637.120805] RIP: 0010:percpu_counter_add_batch+0x4/0x60
>> [12637.120807] Code: 89 e6 89 c7 e8 dd 3b 28 00 3b 05 fb e0 b6 00 72 d8 4c 89 ee 48 89 ef e8 7a 63 2a 00 48 89 d8 5b 5d 41 5c 41 5d c3 41 54 55 53 <48> 8b 47 20 65 44 8b 20 49 63 ec 48 63 ca 48 01 f5 48 39 e9 7e 0a
>> [12637.120809] RSP: 0018:ffff9d1b00a0bd20 EFLAGS: 00010006
>> [12637.120811] RAX: 0000000000000002 RBX: 0000000000000000 RCX: 0000000000000018
>> [12637.120812] RDX: 0000000000000018 RSI: 0000000000000001 RDI: 0000000000000088
>> [12637.120814] RBP: ffff8df67a2988d0 R08: 0000000000000000 R09: ffff8df66fe0cfe0
>> [12637.120815] R10: 0000000000000230 R11: 0000000000000000 R12: 0000000000000000
>> [12637.120816] R13: ffff8df67a298758 R14: ffff8df67a2988c8 R15: ffffccd684229a80
>> [12637.120818] FS:  0000000000000000(0000) GS:ffff8df67ba00000(0000) knlGS:0000000000000000
>> [12637.120820] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [12637.120821] CR2: 00000000000000a8 CR3: 0000000138e0a000 CR4: 0000000000340ef0