v4l2loopback kernel module not loadable

[Michael Johnson]

After installing the v4l2loopback-dkms module, I am not able to load it into the kernel. Attempting to load the module results in the following:

$ sudo modprobe -v v4l2loopback
insmod /lib/modules/3.11.0-17-generic/updates/dkms/v4l2loopback.ko
ERROR: could not insert 'v4l2loopback': Bad address

dmesg shows this:

[ 2082.115432] WARNING: CPU: 5 PID: 15140 at /build/buildd/linux-3.11.0/fs/sysfs/file.c:500 sysfs_attr_ns+0x99/0xa0()
[ 2082.115435] sysfs: kobject (null) without dirent
[ 2082.115437] Modules linked in: v4l2loopback(OF+) v4l2_mem2mem videobuf2_core v4l2_common v4l2_int_device videodev parport_pc ppdev bnep rfcomm bluetooth xt_addrtype ipt_MASQUERADE iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack ip_tables x_tables bridge stp llc aufs vesafb joydev snd_hda_codec_hdmi snd_hda_intel snd_hda_codec mxm_wmi snd_hwdep snd_pcm snd_page_alloc snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq snd_seq_device snd_timer fglrx(POF) kvm_amd kvm crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd edac_core snd soundcore k10temp fam15h_power edac_mce_amd sp5100_tco wmi amd_iommu_v2 i2c_piix4 mac_hid microcode psmouse serio_raw lp parport btrfs zlib_deflate libcrc32c hid_generic hid_microsoft usbhid hid raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq raid1 raid0 r8169 mii ahci multipath sata_sil24 libahci linear
[ 2082.115524] CPU: 5 PID: 15140 Comm: modprobe Tainted: PF W O 3.11.0-17-generic #31-Ubuntu
[ 2082.115527] Hardware name: MSI MS-7693/970A-G46 (MS-7693), BIOS V1.11 10/31/2012
[ 2082.115529] 0000000000000009 ffff88025a5c3be8 ffffffff816e7645 ffff88025a5c3c30
[ 2082.115535] ffff88025a5c3c20 ffffffff81061e0d ffffffffa0bbf080 ffff880402052c18
[ 2082.115541] 0000000000000000 0000000000000001 ffff880402052c00 ffff88025a5c3c80
[ 2082.115547] Call Trace:
[ 2082.115554] [<ffffffff816e7645>] dump_stack+0x45/0x56
[ 2082.115560] [<ffffffff81061e0d>] warn_slowpath_common+0x7d/0xa0
[ 2082.115566] [<ffffffff81061e7c>] warn_slowpath_fmt+0x4c/0x50
[ 2082.115573] [<ffffffff81219249>] sysfs_attr_ns+0x99/0xa0
[ 2082.115579] [<ffffffff8121931f>] sysfs_remove_file+0x1f/0x50
[ 2082.115585] [<ffffffff81472047>] device_remove_file+0x17/0x20
[ 2082.115594] [<ffffffffa0bbc256>] free_devices+0x8c/0xed [v4l2loopback]
[ 2082.115601] [<ffffffffa0bc35e3>] init_module+0x5e3/0x1000 [v4l2loopback]
[ 2082.115609] [<ffffffffa0bc3000>] ? 0xffffffffa0bc2fff
[ 2082.115615] [<ffffffff810020fa>] do_one_initcall+0xfa/0x1b0
[ 2082.115621] [<ffffffff810548e3>] ? set_memory_nx+0x43/0x50
[ 2082.115637] [<ffffffff810cc252>] load_module+0x12b2/0x1b80
[ 2082.115644] [<ffffffff810c7fb0>] ? store_uevent+0x40/0x40
[ 2082.115656] [<ffffffff810ccbc2>] SyS_init_module+0xa2/0xf0
[ 2082.115665] [<ffffffff816f74dd>] system_call_fastpath+0x1a/0x1f
[ 2082.115670] ---[ end trace 10c141d73c72f3af ]---

While I don't know exactly what is going on, the easy fix seems to be to pull in the current debian sid package (0.8.0-1) which installs and loads cleanly on my ubuntu 13.10 install. While there is nothing in the changelog that stands out to me, clearly something is different as the debian 0.8.0-1 package works while the ubuntu 0.7.0-1 package does not produce a loadable module.
https://packages.debian.org/sid/all/v4l2loopback-dkms/download

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.