Additional info:
reporter:       libreport-2.2.1
WARNING: CPU: 0 PID: 2523 at fs/sysfs/group.c:216 sysfs_remove_group+0x93/0xa0()
sysfs group ffffffff81cb1300 not found for kobject 'target4:0:0'
Modules linked in: vfat fat usb_storage fuse bnep bluetooth 6lowpan_iphc rfkill ip6t_rpfilter ip6t_REJECT xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw coretemp kvm_intel kvm gspca_spca561 gspca_main videodev media microcode r8169 mii snd_hda_codec_via snd_hda_codec_generic snd_hda_intel snd_hda_codec snd_hwdep snd_seq snd_seq_device snd_pcm iTCO_wdt gpio_ich iTCO_vendor_support lpc_ich mfd_core snd_timer snd shpchp soundcore serio_raw asus_atk0110 acpi_cpufreq uinput binfmt_misc i915 video i2c_algo_bit drm_kms_helper drm ata_generic pata_acpi i2c_core
CPU: 0 PID: 2523 Comm: umount Not tainted 3.14.4-100.fc19.x86_64 #1
Hardware name: System manufacturer System Product Name/P5G41-M LX2/GB, BIOS 0216    12/31/2009
 0000000000000000 0000000096935ea9 ffff880049143b60 ffffffff816ef1d2
 ffff880049143ba8 ffff880049143b98 ffffffff8108a1bd 0000000000000000
 ffffffff81cb1300 ffff880077fb0038 ffff88006f7fb190 ffff8800512cc900
Call Trace:
 [<ffffffff816ef1d2>] dump_stack+0x45/0x56
 [<ffffffff8108a1bd>] warn_slowpath_common+0x7d/0xa0
 [<ffffffff8108a23c>] warn_slowpath_fmt+0x5c/0x80
 [<ffffffff81265548>] ? kernfs_find_and_get_ns+0x48/0x60
 [<ffffffff812641e3>] sysfs_remove_group+0x93/0xa0
 [<ffffffff8146b483>] dpm_sysfs_remove+0x43/0x50
 [<ffffffff81460a75>] device_del+0x45/0x1c0
 [<ffffffff8148ddf7>] scsi_target_reap_usercontext+0x27/0x40
 [<ffffffff810a4e67>] execute_in_process_context+0x67/0x70
 [<ffffffff8148f274>] scsi_target_reap+0xc4/0xf0
 [<ffffffff814912a6>] scsi_device_dev_release_usercontext+0xe6/0x120
 [<ffffffff810a4e67>] execute_in_process_context+0x67/0x70
 [<ffffffff814911bc>] scsi_device_dev_release+0x1c/0x20
 [<ffffffff81460022>] device_release+0x32/0xa0
 [<ffffffff81356057>] kobject_cleanup+0x77/0x1b0
 [<ffffffff81355f10>] kobject_put+0x30/0x60
 [<ffffffff81460347>] put_device+0x17/0x20
 [<ffffffff814825cb>] scsi_device_put+0x3b/0x50
 [<ffffffff81495d90>] scsi_disk_put+0x30/0x50
 [<ffffffff814960f2>] sd_release+0x42/0xd0
 [<ffffffff8122489c>] __blkdev_put+0x16c/0x1a0
 [<ffffffff8122483e>] __blkdev_put+0x10e/0x1a0
 [<ffffffff8122521c>] blkdev_put+0x4c/0x120
 [<ffffffff811ebd64>] kill_block_super+0x44/0x70
 [<ffffffff811ec06d>] deactivate_locked_super+0x3d/0x60
 [<ffffffff811ec636>] deactivate_super+0x46/0x60
 [<ffffffff81208dac>] mntput_no_expire+0xac/0x140
 [<ffffffff8120a37d>] SyS_umount+0x9d/0x110
 [<ffffffff816ff569>] system_call_fastpath+0x16/0x1b

Potential duplicate: bug 1030988