lkml.org 
[lkml]   [2014]   [Oct]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v2] HID: wacom: Prevent potential null dereference after disconnect
From
On Wed, Oct 8, 2014 at 2:40 PM, Dmitry Torokhov
<dmitry.torokhov@gmail.com> wrote:
> On Wed, Oct 08, 2014 at 11:25:42AM -0700, Jason Gerecke wrote:
>> Repeated connect/disconnect cycles under GNOME can trigger an occasional
>> OOPS from within e.g. wacom_led_select_store, presumably due to a timing
>> issue where userspace begins setting a value immediately before the
>> device disconnects and our shared data is whisked away.
>>
>> Signed-off-by: Jason Gerecke <killertofu@gmail.com>
>> ---
>> Changes in v2:
>> * Added in missing escape character
>>
>> drivers/hid/wacom_sys.c | 13 ++++++++++++-
>> 1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c
>> index 8593047..265429b 100644
>> --- a/drivers/hid/wacom_sys.c
>> +++ b/drivers/hid/wacom_sys.c
>> @@ -641,6 +641,9 @@ static ssize_t wacom_led_select_store(struct device *dev, int set_id,
>> unsigned int id;
>> int err;
>>
>> + if (!wacom)
>> + return -ENODEV;
>> +
>
> Strong NAK. If device could disappear before this check it could as well
> disappear after your check.
>
> This patch does not solve anything.
>

I assume I'll want to either disable interrupts or take a lock
depending on if `wacom_remove` is called from within the interrupt
context, but I haven't had to deal with concurrency in the kernel
before so I'm not entirely sure which option (or which primitive if
locking) would be appropriate...

Jason
---
Now instead of four in the eights place /
you’ve got three, ‘Cause you added one /
(That is to say, eight) to the two, /
But you can’t take seven from three, /
So you look at the sixty-fours....

>> err = kstrtouint(buf, 10, &id);
>> if (err)
>> return err;
>
> Thanks.
>
> --
> Dmitry
> --
> To unsubscribe from this list: send the line "unsubscribe linux-input" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2014-10-09 03:02    [W:3.110 / U:0.112 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site