Jiri Kosina wrote:
On Mon, 6 Dec 2010, Valentine Barshak wrote:
A USB HID device can be disconnected at any time.
If this happens right before or while hiddev_ioctl is in progress,
the hiddev_ioctl tries to access invalid hiddev->hid pointer.
When the hid device is disconnected, the hiddev_disconnect()
ends up with a call to hid_device_release() which frees
hid_device, but doesn't set the hiddev->hid pointer to NULL.
If the deallocated memory region has been re-used by the kernel,
this can cause a crash or memory corruption.
Since disconnect can happen at any time, we can't initialize
struct hid_device *hid = hiddev->hid at the beginning of ioctl
and then use it.
This change checks hiddev->exist flag while holding
the existancelock and uses hid_device only if it exists.
The code duplication isn't really particularly nice, but I don't see any
way around it that wouldn't complicate things even more.
I will be applying the patches, thanks.
Thanks!
(BTW your patches didn't reach mail mailbox, I had to dig them out from
mailinglist -- did you receive bounces by any chance?).
Yes, they did bounce.
Thanks,
Val.
Thanks,
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