Warning from v4l2loopback on Linux 5.7

[terencode]

I'm using the module from https://github.com/aramg/droidcam/archive/v1.1.zip

At boot I get the following:

Trying to vfree() nonexistent vm area (000000000275bb10)
WARNING: CPU: 8 PID: 2911 at mm/vmalloc.c:2297 __vunmap+0x6f/0x270
Modules linked in: fuse overlay rfcomm mousedev joydev input_leds bnep hid_generic btusb btrtl btbcm btintel bluetooth sr_mod cdrom usbhid hid ecdh_generic ecc ccm algif_aead uas cbc usb_storage des_generic libdes ecb arc4 algif_skcipher zram msr cmac md4 algif_hash af_alg iwlmvm mac80211 nls_iso8859_1 nls_cp437 vfat fat kvm_amd libarc4 kvm snd_hda_codec_realtek irqbypass iwlwifi snd_hda_codec_generic snd_usb_audio ledtrig_audio snd_hda_codec_hdmi crct10dif_pclmul crc32_pclmul snd_usbmidi_lib ghash_clmulni_intel snd_hda_intel snd_rawmidi snd_seq_device snd_intel_dspcfg snd_hda_codec aesni_intel cfg80211 glue_helper crypto_simd snd_hwdep cryptd snd_hda_core snd_pcm igb ccp snd_timer snd pcspkr soundcore zenpower(OE) rng_core rfkill dca evdev mac_hid gpio_amdpt pinctrl_amd acpi_cpufreq wmi_bmof mxm_wmi vboxnetflt(OE) vboxnetadp(OE) vboxdrv(OE) pkcs8_key_parser ledtrig_timer it87(OE) hwmon_vid i2c_dev i2c_piix4(OE) v4l2loopback_dc(OE) videodev mc sg crypto_user
 asus_wmi_sensors(OE) wmi ip_tables x_tables ext4 crc32c_generic crc16 mbcache jbd2 crc32c_intel xhci_pci xhci_hcd amdgpu gpu_sched i2c_algo_bit ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops cec rc_core drm agpgart
CPU: 8 PID: 2911 Comm: Discord Tainted: G           OE     5.7.0-2-tkg-bmq #1
Hardware name: System manufacturer System Product Name/CROSSHAIR VI HERO, BIOS 7704 12/16/2019
RIP: 0010:__vunmap+0x6f/0x270
Code: 4c 3b 6b f0 73 31 48 8b 5b 10 48 85 db 75 f1 48 c7 c7 a4 0e 2e b1 e8 00 18 6f 00 4c 89 ee 48 c7 c7 d0 43 90 b0 e8 d8 38 e5 ff <0f> 0b 5b 5d 41 5c 41 5d 41 5e 41 5f c3 4c 3b 6b f8 72 06 48 8b 5b
RSP: 0018:ffffb27783a33e60 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000007
RDX: 00000000fffffff8 RSI: 0000000000000092 RDI: ffff8fd8cec19a00
RBP: 0000000000000000 R08: 00000000000005f4 R09: 0000000000000003
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000001
R13: ffffb27788001000 R14: ffff8fd8cca2d080 R15: ffff8fd8cc7b9420
FS:  00007f5219ab7c80(0000) GS:ffff8fd8cec00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055bc30e1fc30 CR3: 00000003451be000 CR4: 0000000000340ee0
Call Trace:
 v4l2_loopback_close+0x86/0xf0 [v4l2loopback_dc]
 v4l2_release+0xb8/0xc0 [videodev]
 __fput+0xca/0x230
 task_work_run+0x5f/0x80
 prepare_exit_to_usermode+0x1ac/0x1d0
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f521c29c90b
Code: 03 00 00 00 0f 05 48 3d 00 f0 ff ff 77 41 c3 48 83 ec 18 89 7c 24 0c e8 f3 fb ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 31 fc ff ff 8b 44
RSP: 002b:00007fff010d0a70 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 00003bdbc0193b40 RCX: 00007f521c29c90b
RDX: 0000000000000008 RSI: 0000000000000017 RDI: 0000000000000017
RBP: 00007fff010d0b90 R08: 0000000000000000 R09: 00007fff010d0ab8
R10: 0000000000000008 R11: 0000000000000293 R12: 00003bdbc0160ae0
R13: 00007fff010d0af8 R14: 0000000000000017 R15: 00003bdbc014af90

It does not seem to happen all the time or I don't know how to trigger it.

[aramg]

A lot of the kernels updates introduce v4l2 breakages. Will look when I get a chance.
Also worth keeping an eye on the main v4l2loopback repo.

[aramg]

See #56 on why the fork exists

[terencode]

Just happened again on 5.8.0 after a resume from suspend to ram:

------------[ cut here ]------------
Trying to vfree() nonexistent vm area (00000000002b9aa9)
WARNING: CPU: 10 PID: 272888 at mm/vmalloc.c:2283 __vunmap+0x6f/0x270
Modules linked in: fuse overlay rfcomm joydev input_leds mousedev bnep hid_generic btusb btrtl btbcm btintel bluetooth snd_usb_audio usbhid snd_usbmidi_lib hid ecdh_generic snd_rawmidi ecc snd_seq_device ccm algif_aead cbc des_generic libdes ecb arc4 algif_skcipher cmac md4 uas cpufreq_ondemand algif_hash usb_storage msr af_alg iwlmvm mac80211 snd_hda_codec_realtek libarc4 snd_hda_codec_generic snd_hda_codec_hdmi ledtrig_audio edac_mce_amd nls_iso8859_1 nls_cp437 kvm_amd snd_hda_intel vfat fat snd_intel_dspcfg kvm iwlwifi snd_hda_codec irqbypass snd_hda_core snd_hwdep crct10dif_pclmul crc32_pclmul snd_pcm ghash_clmulni_intel aesni_intel snd_timer crypto_simd ccp cryptd snd glue_helper cfg80211 igb soundcore rng_core rapl i2c_piix4 pcspkr zenpower(OE) rfkill dca evdev gpio_amdpt pinctrl_amd mac_hid acpi_cpufreq wmi_bmof mxm_wmi pkcs8_key_parser i2c_dev ledtrig_timer it87(OE) hwmon_vid v4l2loopback_dc(OE) videodev mc sg crypto_user asus_wmi_sensors(OE) wmi ip_tables x_tables ext4
 crc32c_generic crc16 mbcache jbd2 amdgpu crc32c_intel xhci_pci xhci_pci_renesas xhci_hcd gpu_sched i2c_algo_bit ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops cec rc_core drm agpgart
CPU: 10 PID: 272888 Comm: Discord Tainted: G        W  OE     5.8.0-arch1-1 #1
Hardware name: System manufacturer System Product Name/CROSSHAIR VI HERO, BIOS 7803 06/17/2020
RIP: 0010:__vunmap+0x6f/0x270
Code: 4c 3b 6b f0 73 31 48 8b 5b 10 48 85 db 75 f1 48 c7 c7 14 56 76 a7 e8 b0 b9 78 00 4c 89 ee 48 c7 c7 68 a6 b7 a6 e8 57 84 e1 ff <0f> 0b 5b 5d 41 5c 41 5d 41 5e 41 5f c3 4c 3b 6b f8 72 06 48 8b 5b
RSP: 0018:ffffb3ec49c57e50 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000001 RSI: ffffffffa6b695d7 RDI: 00000000ffffffff
RBP: 0000000000000000 R08: 0000000000000760 R09: 0000000000000003
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000001
R13: ffffb3ec60001000 R14: ffff9c8a8c847b00 R15: ffff9c8a8ba73ea0
FS:  00007f49160d2140(0000) GS:ffff9c8a8ec80000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00001325b8876008 CR3: 00000003ea2f6000 CR4: 0000000000340ee0
Call Trace:
 v4l2_loopback_close+0x86/0xf0 [v4l2loopback_dc]
 v4l2_release+0xb8/0xc0 [videodev]
 __fput+0xca/0x230
 task_work_run+0x5c/0x90
 __prepare_exit_to_usermode+0x198/0x1c0
 do_syscall_64+0x50/0x70
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f491896e90b
Code: 03 00 00 00 0f 05 48 3d 00 f0 ff ff 77 41 c3 48 83 ec 18 89 7c 24 0c e8 f3 fb ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 31 fc ff ff 8b 44
RSP: 002b:00007fff03fb9c10 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 00001325b889cb80 RCX: 00007f491896e90b
RDX: 0000000000000008 RSI: 0000000000000017 RDI: 0000000000000017
RBP: 00007fff03fb9d30 R08: 0000000000000000 R09: 00007fff03fb9c58
R10: 0000000000000008 R11: 0000000000000293 R12: 00001325b886cb20
R13: 00007fff03fb9c98 R14: 0000000000000017 R15: 00001325b883f0c0
---[ end trace b2008fd5000b35b4 ]---

[vmandal]

I am not able to boot:
Failed to start Load Kernel Modules.
Failed to find module 'v4l2loopback_dc'

Ruining the uninstall scipt did not help

$ sudo /opt/droidcam-uninstall
Un-loading driver module
rmmod: ERROR: Module v4l2loopback_dc is not currently loaded
Removing files
Cleaning configs
Done

My OS: CentOS Linux release 7.8.2003 (Core)
kernel version 3.10.0-1127.19.1.el7.x86_64

[aramg]

This issue is about Linux 5.7, you have 3.1. Can you email dev47apps at gmail.com for support please.

[jamestmartin]

Uname Linux jazz 6.1.0-7-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.20-1 (2023-03-19) x86_64 GNU/Linux.

The error includes in a loop, happening after 3 seconds, then after 15 seconds, and then after 3 seconds again. It continues in this pattern until it has eaten up all of my 32 GB of RAM and crashes my system after about 16 hours. This is what htop looks like 5 and a half hours in. 18.8G used with no applications open, without having ever attached my phone or running droidcam.

This is as much as dmesg saved when I piped it into a file: trying_to_vfree_nonexistent_vm_area.txt