Access to some folders hangs and in dmesg see kernel BUG report

[Vadim Shalts]

Probably freeze during access to folder caused by
kernel BUG at /build/linux-BvkamA/linux-4.4.0/fs/namei.c:2562!

Also segfault during collecting information with 'ubuntu-bug linux', but not sure it is related:
[80059.937844] apport-kde[22602]: segfault at 7fdb0f1d4b00 ip 00007fdb44cd40f5 sp 00007ffd35400828 error 4 in QtCore.cpython-35m-x86_64-linux-gnu.so[7fdb44ae4000+268000]
[80099.437691] Qt bearer threa[23986]: segfault at 7f23b89942e9 ip 00007f23b3d41ccb sp 00007f239fffce50 error 4 in libgcc_s.so.1[7f23b3d33000+16000]
It is looks like separate issue.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-28-generic 4.4.0-28.47
ProcVersionSignature: Ubuntu 4.4.0-28.47-generic 4.4.13
Uname: Linux 4.4.0-28-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: vadim 4045 F.... pulseaudio
 /dev/snd/controlC0: vadim 4045 F.... pulseaudio
Date: Thu Sep 22 13:52:19 2016
EcryptfsInUse: Yes
HibernationDevice: RESUME=UUID=4ff5857a-eca8-4968-9e7d-16cb2b146f60
InstallationDate: Installed on 2015-04-28 (512 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
MachineType: ASUS All Series
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-28-generic root=UUID=f0d3e2ee-9f79-431c-9d8a-1079d7638279 ro quiet splash vt.handoff=7
PulseList:
 Error: command ['pacmd', 'list'] failed with exit code 1: Home directory not accessible: Permission denied
 No PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
 linux-restricted-modules-4.4.0-28-generic N/A
 linux-backports-modules-4.4.0-28-generic N/A
 linux-firmware 1.157.3
RfKill:

SourcePackage: linux
UpgradeStatus: Upgraded to xenial on 2016-04-22 (152 days ago)
dmi.bios.date: 08/12/2014
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 1002
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: H81M-K
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: Rev X.0x
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr1002:bd08/12/2014:svnASUS:pnAllSeries:pvrSystemVersion:rvnASUSTeKCOMPUTERINC.:rnH81M-K:rvrRevX.0x:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.name: All Series
dmi.product.version: System Version
dmi.sys.vendor: ASUS

[Brad Figg (brad-figg)]

This change was made by a bot.

[Joseph Salisbury (jsalisbury)]

Did this issue start happening after an update/upgrade? Was there a prior kernel version where you were not having this particular problem?

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.8 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.8

[Vadim Shalts (vshalts)]

Unfortunately I don't monitor precisely kernel version and updates. Hard to say in what state was system prior to current one.

And I don't have strong scenario to reproduce this issue. But it hit me be several times. I know cases in with it looks like appear. Switched to upstream kernel. So far so good. Will continue to monitoring. If I will not be able to reproduce this issue during next week then I will mark bug with 'kernel-fixed-upstream'.

[Vadim Shalts (vshalts)]

As far as I can tell it is fixed in upstream. And this bug already marked as "Confirmed" if I am understand this correctly.

[Vadim Shalts (vshalts)]

Nope, was wrong. It is broken in upstream too. My system:

Linux vshalts_da.vshalts.com 4.8.0-040800-generic #201610022031 SMP Mon Oct 3 00:32:57 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

Fresh dmesg error:

[276405.098149] ------------[ cut here ]------------
[276405.098172] kernel BUG at /home/kernel/COD/linux/fs/namei.c:2777!
[276405.098188] invalid opcode: 0000 [#1] SMP
[276405.098199] Modules linked in: cpuid ppp_async ppp_generic slhc fuse ipt_REJECT nf_reject_ipv4 nf_log_ipv4 xt_recent nf_conntrack_ipv6 nf_defrag_ipv6 xt_conntrack ip6t_REJECT nf_reject_ipv6 nf_log_ipv6 nf_log_common xt_LOG xt_limit xt_hashlimit ip6table_filter ip6_tables xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack xt_tcpudp pci_stub vboxpci(OE) vboxnetadp(OE) vboxnetflt(OE) vboxdrv(OE) bridge stp llc iptable_filter ip_tables x_tables binfmt_misc dm_crypt dm_mod ecb intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp snd_hda_codec_realtek snd_hda_codec_generic uvcvideo snd_hda_intel videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 snd_hda_codec videobuf2_core snd_usb_audio snd_hda_core videodev
[276405.098426] snd_usbmidi_lib media snd_hwdep snd_pcm snd_seq_midi snd_seq_midi_event snd_rawmidi joydev eeepc_wmi kvm_intel asus_wmi sparse_keymap rfkill kvm irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel snd_seq snd_seq_device snd_timer aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd intel_cstate intel_rapl_perf snd serio_raw mei_me sg lpc_ich mei shpchp soundcore battery evdev tpm_infineon ecryptfs parport_pc ppdev lp parport autofs4 ext4 crc16 jbd2 fscrypto mbcache hid_generic usbhid hid btrfs xor raid6_pq i915 i2c_algo_bit drm_kms_helper syscopyarea crc32c_intel sysfillrect psmouse sysimgblt fb_sys_fops drm ahci r8169 libahci mii wmi thermal fan button fjes video
[276405.098660] CPU: 0 PID: 24246 Comm: rm Tainted: G W OE 4.8.0-040800-generic #201610022031
[276405.098684] Hardware name: ASUS All Series/H81M-K, BIOS 1002 08/12/2014
[276405.098701] task: ffff94ab72632a80 task.stack: ffff94a9fd41c000
[276405.098717] RIP: 0010:[<ffffffff92c20db4>] [<ffffffff92c20db4>] may_delete+0x154/0x170
[276405.098742] RSP: 0018:ffff94a9fd41fdf0 EFLAGS: 00010216
[276405.098757] RAX: ffff94ab9015dc00 RBX: ffff94aa28be2000 RCX: 0000000e00000000
[276405.098775] RDX: 0000000000000000 RSI: ffff94aa28be2000 RDI: ffff94aa06ec3bf8
[276405.098793] RBP: ffff94ab6a7e8520 R08: ffff94ab91a4a800 R09: ffff94aadbc6308b
[276405.098811] R10: ffff94aabf9206f8 R11: 18c23f265c15f699 R12: ffff94aa06ec3bf8
[276405.098830] R13: ffff94a9e0e7a6e0 R14: ffff94a9afe5e800 R15: 0000000000000000
[276405.098848] FS: 00007fa4589ce700(0000) GS:ffff94ab9fa00000(0000) knlGS:0000000000000000
[276405.098868] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[276405.098883] CR2: 0000000000f721c8 CR3: 0000000207fc6000 CR4: 00000000001406f0
[276405.098900] Stack:
[276405.098908] ffff94aa28be2000 ffff94a9fd41fe90 ffff94aa06ec3bf8 ffff94a9e0e7a6e0
[276405.098932] ffff94a9afe5e800 ffffffff92c21de3 ffff94aa28be2000 ffff94a9fd41fe90
[276405.098955] ffff94ab9015dc00 ffff94a9acc05c00 ffff...