Sorry this only seems reproducible in a scenario a USB switch or cable that
doesn't support enough amps for the device.  Any device or webcam which
overloads its power supply and then disconnects during UVC initialization
will disconnect itself during a critical period in the kernel where an
interrupt is not expected.  The interrupt will trigger an unexpected
disconnect and crash the USB module.  The patch was rejected for this by
the USB module maintainers.

JohnnyB

On Sat, Jan 15, 2022 at 2:55 PM Paul Menzel <email address hidden>
wrote:

> I read at [1] about the issue.
>
> @kaihengfeng, I suggest to send the patch upstream for review even with
> no tests. Maybe there will be testers on the Linux kernel mailing list.
>
> [1]: https://etbe.coker.com.au/2022/01/09/video-conferencing-lca/
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1827452
>
> Title:
>   null pointer dereference in uvcvideo
>
> Status in linux package in Ubuntu:
>   Expired
>
> Bug description:
>   I have a logitech c920 webcam. When using this camera in obs-studio
>   v23.x, all of my USB devices stop working and I see the following in
>   my kernel log:
>
>   [  590.282211] usb 3-3: new high-speed USB device number 5 using xhci_hcd
>   [  592.660916] usb 3-3: New USB device found, idVendor=046d,
> idProduct=082d, bcdDevice= 0.11
>   [  592.660922] usb 3-3: New USB device strings: Mfr=0, Product=2,
> SerialNumber=1
>   [  592.660925] usb 3-3: Product: HD Pro Webcam C920
>   [  592.660928] usb 3-3: SerialNumber: 2EAD866F
>   [  592.664600] uvcvideo: Found UVC 1.00 device HD Pro Webcam C920
> (046d:082d)
>   [  592.666416] uvcvideo 3-3:1.0: Entity type for entity Processing 3 was
> not initialized!
>   [  592.666421] uvcvideo 3-3:1.0: Entity type for entity Extension 6 was
> not initialized!
>   [  592.666425] uvcvideo 3-3:1.0: Entity type for entity Extension 12 was
> not initialized!
>   [  592.666428] uvcvideo 3-3:1.0: Entity type for entity Camera 1 was not
> initialized!
>   [  592.666430] uvcvideo 3-3:1.0: Entity type for entity Extension 8 was
> not initialized!
>   [  592.666433] uvcvideo 3-3:1.0: Entity type for entity Extension 9 was
> not initialized!
>   [  592.666436] uvcvideo 3-3:1.0: Entity type for entity Extension 10 was
> not initialized!
>   [  592.666439] uvcvideo 3-3:1.0: Entity type for entity Extension 11 was
> not initialized!
>   [  592.666622] input: HD Pro Webcam C920 as
> /devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3:1.0/input/input23
>   [  748.490453] usb 3-3: reset high-speed USB device number 5 using
> xhci_hcd
>   [  938.125745] usb 3-3: USB disconnect, device number 5
>   [  943.298530] BUG: unable to handle kernel NULL pointer dereference at
> 0000000000000000
>   [  943.298533] #PF error: [normal kernel read fault]
>   [  943.298534] PGD 80000007ca5f3067 P4D 80000007ca5f3067 PUD 0
>   [  943.298536] Oops: 0000 [#1] SMP PTI
>   [  943.298538] CPU: 0 PID: 9442 Comm: libobs: graphic Tainted: P
>    OE     5.0.0-13-generic #14-Ubuntu
>   [  943.298539] Hardware name: Gigabyte Technology Co., Ltd.
> Z87-HD3/Z87-HD3, BIOS F7 01/20/2014
>   [  943.298543] RIP: 0010:usb_ifnum_to_if+0x24/0x60
>   [  943.298544] Code: ff c3 0f 1f 40 00 0f 1f 44 00 00 55 48 8b 87 c0 03
> 00 00 48 89 e5 48 85 c0 74 43 0f b6 48 04 84 c9 74 39 48 8b 90 98 00 00 00
> <48> 8b 3a 0f b6 7f 02 39 fe 74 2b 48 8d 90 a0 00 00 00 8d 41 ff 48
>   [  943.298545] RSP: 0018:ffffbdae493dbab0 EFLAGS: 00010202
>   [  943.298547] RAX: ffffa106ae527000 RBX: ffffa1070ad0a800 RCX:
> 0000000000000004
>   [  943.298547] RDX: 0000000000000000 RSI: 0000000000000001 RDI:
> ffffa1070ad0a800
>   [  943.298548] RBP: ffffbdae493dbab0 R08: 0000000000027040 R09:
> ffffffffb57825b8
>   [  943.298549] R10: fffffba45fce4bc0 R11: 0000000000000001 R12:
> 0000000000000000
>   [  943.298550] R13: ffffa10644187b98 R14: 00000000ffffff92 R15:
> ffffa1075131a000
>   [  943.298551] FS:  00007f93c40d7700(0000) GS:ffffa1075ea00000(0000)
> knlGS:0000000000000000
>   [  943.298552] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   [  943.298553] CR2: 0000000000000000 CR3: 00000006f8a94004 CR4:
> 00000000001606f0
>   [  943.298553] Call Trace:
>   [  943.298557]  usb_hcd_alloc_bandwidth+0x241/0x370
>   [  943.298559]  usb_set_interface+0xfc/0x380
>   [  943.298565]  uvc_video_start_transfer+0x155/0x4b0 [uvcvideo]
>   [  943.298568]  uvc_video_start_streaming+0x7f/0xd0 [uvcvideo]
>   [  943.298570]  uvc_start_streaming+0x28/0x70 [uvcvideo]
>   [  943.298573]  vb2_start_streaming+0x6d/0x110 [videobuf2_common]
>   [  943.298575]  vb2_core_streamon+0x59/0xc0 [videobuf2_common]
>   [  943.298578]  vb2_streamon+0x18/0x30 [videobuf2_v4l2]
>   [  943.298580]  uvc_queue_streamon+0x2e/0x50 [uvcvideo]
>   [  943.298582]  uvc_ioctl_streamon+0x3f/0x60 [uvcvideo]
>   [  943.298588]  v4l_streamon+0x20/0x30 [videodev]
>   [  943.298592]  __video_do_ioctl+0x19a/0x3f0 [videodev]
>   [  943.298596]  video_usercopy+0x1a6/0x660 [videodev]
>   [  943.298599]  ? v4l_s_fmt+0x630/0x630 [videodev]
>   [  943.298603]  video_ioctl2+0x15/0x20 [videodev]
>   [  943.298606]  v4l2_ioctl+0x49/0x50 [videodev]
>   [  943.298608]  do_vfs_ioctl+0xa9/0x640
>   [  943.298610]  ? __switch_to_asm+0x34/0x70
>   [  943.298611]  ? __switch_to_asm+0x40/0x70
>   [  943.298612]  ? __switch_to_asm+0x34/0x70
>   [  943.298612]  ? __switch_to_asm+0x40/0x70
>   [  943.298613]  ? __switch_to_asm+0x34/0x70
>   [  943.298614]  ? __switch_to_asm+0x40/0x70
>   [  943.298615]  ? __switch_to_asm+0x34/0x70
>   [  943.298616]  ? __switch_to_asm+0x40/0x70
>   [  943.298617]  ksys_ioctl+0x67/0x90
>   [  943.298619]  __x64_sys_ioctl+0x1a/0x20
>   [  943.298621]  do_syscall_64+0x5a/0x110
>   [  943.298622]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>   [  943.298623] RIP: 0033:0x7f9430e082e9
>   [  943.298624] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00
> 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05
> <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 77 cb 0c 00 f7 d8 64 89 01 48
>   [  943.298625] RSP: 002b:00007f93c40d6428 EFLAGS: 00000246 ORIG_RAX:
> 0000000000000010
>   [  943.298626] RAX: ffffffffffffffda RBX: 00007f94000da020 RCX:
> 00007f9430e082e9
>   [  943.298627] RDX: 00007f93c40d6444 RSI: 0000000040045612 RDI:
> 000000000000003b
>   [  943.298628] RBP: 0000000000000000 R08: 00000000c058560f R09:
> 000055f3e344a6e0
>   [  943.298629] R10: 0000000000000000 R11: 0000000000000246 R12:
> 000000000000003b
>   [  943.298629] R13: 00007f93c40d68bc R14: 00007f94000da020 R15:
> 0000000000000000
>   [  943.298631] Modules linked in: uvcvideo videobuf2_vmalloc
> videobuf2_memops videobuf2_v4l2 videobuf2_common snd_usb_audio videodev
> snd_usbmidi_lib media rfcomm joydev input_leds hid_generic uhid hid
> algif_hash algif_skcipher af_alg nf_conntrack_netlink nfnetlink xfrm_user
> xfrm_algo xt_addrtype xt_conntrack br_netfilter veth ebtable_filter
> ebtables ip6t_MASQUERADE ip6table_nat nf_nat_ipv6 ip6table_filter
> ip6_tables ipt_MASQUERADE xt_CHECKSUM xt_comment xt_tcpudp iptable_nat
> nf_nat_ipv4 nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4
> iptable_mangle iptable_filter bpfilter bridge stp llc aufs overlay pci_stub
> vboxpci(OE) vboxnetadp(OE) vboxnetflt(OE) cmac bnep vboxdrv(OE) binfmt_misc
> nvidia_uvm(OE) nls_iso8859_1 intel_rapl x86_pkg_temp_thermal
> intel_powerclamp kvm_intel kvm irqbypass snd_hda_codec_hdmi
> crct10dif_pclmul crc32_pclmul ghash_clmulni_intel nvidia_drm(POE)
> nvidia_modeset(POE) arc4 btusb btrtl btbcm btintel nvidia(POE)
> snd_hda_codec_realtek bluetooth aesni_intel
>   [  943.298652]  snd_hda_codec_generic ledtrig_audio aes_x86_64
> snd_hda_intel crypto_simd snd_hda_codec cryptd ecdh_generic glue_helper
> iwlmvm snd_hda_core mac80211 snd_hwdep snd_pcm intel_cstate intel_rapl_perf
> snd_seq_midi snd_seq_midi_event snd_rawmidi iwlwifi drm_kms_helper drm
> snd_seq ipmi_devintf ipmi_msghandler fb_sys_fops syscopyarea snd_seq_device
> sysfillrect cfg80211 snd_timer sysimgblt snd soundcore mei_me mei mac_hid
> sch_fq_codel it87 hwmon_vid coretemp parport_pc ppdev lp parport ip_tables
> x_tables autofs4 xfs raid10 raid456 async_raid6_recov async_memcpy async_pq
> async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear
> dm_mirror dm_region_hash dm_log i2c_i801 ahci lpc_ich libahci r8169 realtek
> video
>   [  943.298672] CR2: 0000000000000000
>   [  943.298674] ---[ end trace 62d503b51a37a64a ]---
>   [  943.298675] RIP: 0010:usb_ifnum_to_if+0x24/0x60
>   [  943.298676] Code: ff c3 0f 1f 40 00 0f 1f 44 00 00 55 48 8b 87 c0 03
> 00 00 48 89 e5 48 85 c0 74 43 0f b6 48 04 84 c9 74 39 48 8b 90 98 00 00 00
> <48> 8b 3a 0f b6 7f 02 39 fe 74 2b 48 8d 90 a0 00 00 00 8d 41 ff 48
>   [  943.298677] RSP: 0018:ffffbdae493dbab0 EFLAGS: 00010202
>   [  943.298678] RAX: ffffa106ae527000 RBX: ffffa1070ad0a800 RCX:
> 0000000000000004
>   [  943.298679] RDX: 0000000000000000 RSI: 0000000000000001 RDI:
> ffffa1070ad0a800
>   [  943.298680] RBP: ffffbdae493dbab0 R08: 0000000000027040 R09:
> ffffffffb57825b8
>   [  943.298680] R10: fffffba45fce4bc0 R11: 0000000000000001 R12:
> 0000000000000000
>   [  943.298681] R13: ffffa10644187b98 R14: 00000000ffffff92 R15:
> ffffa1075131a000
>   [  943.298682] FS:  00007f93c40d7700(0000) GS:ffffa1075ea00000(0000)
> knlGS:0000000000000000
>   [  943.298683] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   [  943.298684] CR2: 0000000000000000 CR3: 00000006f8a94004 CR4:
> 00000000001606f0
>
>   Interestingly, this doesn't crash the machine, but it does seem to
>   crash udev or whatever is responsible for updating USB device state,
>   as I've disconnected the webcam but running lsusb still shows it as
>   connected. This is something of a pain as the only way I could file
>   this report was to ssh in from another machine with X forwarding
>   enabled, as my keyboard and mouse no longer function.
>
>   Note that sometimes OBS will work fine with this camera, however this
>   bug will still occur when I attempt to change the camera resolution.
>
>   ProblemType: Bug
>   DistroRelease: Ubuntu 19.04
>   Package: linux-modules-extra-5.0.0-13-generic 5.0.0-13.14
>   ProcVersionSignature: Ubuntu 5.0.0-13.14-generic 5.0.6
>   Uname: Linux 5.0.0-13-generic x86_64
>   NonfreeKernelModules: nvidia_modeset nvidia
>   ApportVersion: 2.20.10-0ubuntu27
>   Architecture: amd64
>   AudioDevicesInUse:
>    USER        PID ACCESS COMMAND
>    /dev/snd/controlC1:  bburns     3961 F.... pulseaudio
>    /dev/snd/pcmC1D7p:   bburns     3961 F...m pulseaudio
>    /dev/snd/controlC0:  bburns     3961 F.... pulseaudio
>    /dev/snd/pcmC0D1c:   bburns     3961 F...m pulseaudio
>   Date: Thu May  2 18:47:59 2019
>   HibernationDevice: RESUME=none
>   InstallationDate: Installed on 2018-07-30 (276 days ago)
>   InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64
> (20180725)
>   MachineType: Gigabyte Technology Co., Ltd. Z87-HD3
>   ProcEnviron:
>    TERM=xterm-256color
>    PATH=(custom, no user)
>    XDG_RUNTIME_DIR=<set>
>    LANG=en_US.UTF-8
>    SHELL=/bin/bash
>   ProcFB: 0 EFI VGA
>   ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.0.0-13-generic
> root=/dev/mapper/cl_box-root ro
>   RelatedPackageVersions:
>    linux-restricted-modules-5.0.0-13-generic N/A
>    linux-backports-modules-5.0.0-13-generic  N/A
>    linux-firmware                            1.178
>   SourcePackage: linux
>   UpgradeStatus: Upgraded to disco on 2019-04-24 (8 days ago)
>   dmi.bios.date: 01/20/2014
>   dmi.bios.vendor: American Megatrends Inc.
>   dmi.bios.version: F7
>   dmi.board.asset.tag: To be filled by O.E.M.
>   dmi.board.name: Z87-HD3
>   dmi.board.vendor: Gigabyte Technology Co., Ltd.
>   dmi.board.version: To be filled by O.E.M.
>   dmi.chassis.asset.tag: To Be Filled By O.E.M.
>   dmi.chassis.type: 3
>   dmi.chassis.vendor: Gigabyte Technology Co., Ltd.
>   dmi.chassis.version: To Be Filled By O.E.M.
>   dmi.modalias:
> dmi:bvnAmericanMegatrendsInc.:bvrF7:bd01/20/2014:svnGigabyteTechnologyCo.,Ltd.:pnZ87-HD3:pvrTobefilledbyO.E.M.:rvnGigabyteTechnologyCo.,Ltd.:rnZ87-HD3:rvrTobefilledbyO.E.M.:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvrToBeFilledByO.E.M.:
>   dmi.product.family: To be filled by O.E.M.
>   dmi.product.name: Z87-HD3
>   dmi.product.sku: To be filled by O.E.M.
>   dmi.product.version: To be filled by O.E.M.
>   dmi.sys.vendor: Gigabyte Technology Co., Ltd.
>
> To manage notifications about this bug go to:
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>
>