• Fernando Luis Vázquez Cao's avatar
    HID: hidraw: fix warning destroying hidraw device files after parent · 47587fc0
    Fernando Luis Vázquez Cao authored
    I noticed that after hot unplugging a Logitech unifying receiver
    (drivers/hid/hid-logitech-dj.c) the kernel would occasionally spew a
    stack trace similar to this:
    
    usb 1-1.1.2: USB disconnect, device number 7
    WARNING: CPU: 0 PID: 2865 at fs/sysfs/group.c:216 device_del+0x40/0x1b0()
    sysfs group ffffffff8187fa20 not found for kobject 'hidraw0'
    [...]
    CPU: 0 PID: 2865 Comm: upowerd Tainted: G        W 3.14.0-rc4 #7
    Hardware name: LENOVO 7783PN4/        , BIOS 9HKT43AUS 07/11/2011
     0000000000000009 ffffffff814cd684 ffff880427ccfdf8 ffffffff810616e7
     ffff88041ec61800 ffff880427ccfe48 ffff88041e444d80 ffff880426fab8e8
     ffff880429359960 ffffffff8106174c ffffffff81714b98 0000000000000028
    Call Trace:
     [<ffffffff814cd684>] ? dump_stack+0x41/0x51
     [<ffffffff810616e7>] ? warn_slowpath_common+0x77/0x90
     [<ffffffff8106174c>] ? warn_slowpath_fmt+0x4c/0x50
     [<ffffffff81374fd0>] ? device_del+0x40/0x1b0
     [<ffffffff8137516f>] ? device_unregister+0x2f/0x50
     [<ffffffff813751fa>] ? device_destroy+0x3a/0x40
     [<ffffffffa03ca245>] ? drop_ref+0x55/0x120 [hid]
     [<ffffffffa03ca3e6>] ? hidraw_release+0x96/0xb0 [hid]
     [<ffffffff811929da>] ? __fput+0xca/0x210
     [<ffffffff8107fe17>] ? task_work_run+0x97/0xd0
     [<ffffffff810139a9>] ? do_notify_resume+0x69/0xa0
     [<ffffffff814dbd22>] ? int_signal+0x12/0x17
    ---[ end trace 63f4a46f6566d737 ]---
    
    During device removal hid_disconnect() is called via hid_hw_stop() to
    stop the device and free all its resources, including the sysfs
    files. The problem is that if a user space process, such as upowerd,
    holds a reference to a hidraw file the corresponding sysfs files will
    be kept around (drop_ref() does not call device_destroy() if the open
    counter is not 0) and it will be usb_disconnect() who, by calling
    device_del() for the USB device, will indirectly remove the sysfs
    files of the hidraw device (sysfs_remove_dir() is recursive these
    days). Because of this, by the time user space releases the last
    reference to the hidraw file and drop_ref() tries to destroy the
    device the sysfs files are already gone and the kernel will print
    the warning above.
    
    Fix this by calling device_destroy() at USB disconnect time.
    Signed-off-by: default avatarFernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
    Reviewed-by: default avatarDavid Herrmann <dh.herrmann@gmail.com>
    Cc: stable@vger.kernel.org	# 3.13
    Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
    47587fc0
hidraw.c 13.5 KB