Am Dienstag, den 15.08.2017, 15:59 +0300 schrieb Anton Volkov:
> Hello.
>
> While searching for races in the Linux kernel I've come across
> "drivers/usb/misc/adutux.ko" module. Here is a question that I came up
> with while analyzing results. Lines are given using the info from Linux
> v4.12.
>
> Consider the following case:
>
> Thread 1: Thread 2:
> adu_release
> ->adu_release_internal adu_disconnect
> <READ &dev->udev->dev> dev->udev = NULL
> (adutux.c: line 298) (adutux.c: line 771)
> usb_deregister_dev
>
> Comments in the source code point at the possibility of adu_release()
> being called separately from adu_disconnect(). adu_release() and
> adu_disconnect() acquire different mutexes, so they are not protected
> from one another. If adu_disconnect() changes dev->udev before its value
> is read in adu_release_internal() there will be a NULL pointer
> dereference on a read attempt. Is this case feasible from your point of
> view?
>
> Thank you for your time.
Hi,
your analysis seems correct to me. In fact it looks like
66d4bc30d128e7c7ac4cf64aa78cb76e971cec5b
USB: adutux: remove custom debug macro
more or less broke disconnect on this driver
(the URBs can also finish after dev->udev = NULL)
Do you want to do a fix or do you want me to do it?
Regards
Oliver
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