Hi Fernando,
Why are older kernels not affected ?
-nestor
On Wed, Feb 26, 2014 at 8:56 AM, Fernando Luis Vázquez Cao
<fernando_b1@xxxxxxxxxxxxx> wrote:
> I forgot to mention that if the fix below is acceptable it
> should be queued for 3.13-stable (older kernels are not
> affected).
>
>
> On 02/26/2014 04:51 PM, Fernando Luis Vázquez Cao wrote:
>>
>> 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.
>>
>> Cc: Nestor Lopez Casado <nlopezcasad@xxxxxxxxxxxx>
>> Signed-off-by: Fernando Luis Vazquez Cao <fernando@xxxxxxxxxxxxx>
>> ---
>>
>> diff -urNp linux-3.14-rc4-orig/drivers/hid/hidraw.c
>> linux-3.14-rc4/drivers/hid/hidraw.c
>> --- linux-3.14-rc4-orig/drivers/hid/hidraw.c 2014-02-26
>> 14:21:48.622980475 +0900
>> +++ linux-3.14-rc4/drivers/hid/hidraw.c 2014-02-26 14:22:17.990979556
>> +0900
>> @@ -320,13 +320,13 @@ static void drop_ref(struct hidraw *hidr
>> hid_hw_close(hidraw->hid);
>> wake_up_interruptible(&hidraw->wait);
>> }
>> + device_destroy(hidraw_class,
>> + MKDEV(hidraw_major, hidraw->minor));
>> } else {
>> --hidraw->open;
>> }
>> if (!hidraw->open) {
>> if (!hidraw->exist) {
>> - device_destroy(hidraw_class,
>> - MKDEV(hidraw_major,
>> hidraw->minor));
>> hidraw_table[hidraw->minor] = NULL;
>> kfree(hidraw);
>> } else {
>>
>>
>>
>
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