[vbox-dev] Nullpointer access by USBDevIo thread in vusbUrbDoReapAsync

[Alexander Boettcher]

Hello,

we encountered in our ported version of Virtualbox (originally in
5.1.22, now in 5.1.32) from time to time a nullpointer crash in the
context of the USBDevIo thread (vusbUrbDoReapAsync() function).

We get around by the following patch [1] (original bug report at [2])
and all seems to work as expected.

The question from my side is, do you think this is valid fix ? Or do you
expect that pVUsbUrbNext should never be null and it maybe just becomes
null possibly due to our porting (timing, wrong usage etc.) ?

After looking through your svn repository at [0] it seems the issue also
could possibly exists there, since the code looks very similar regarding
the pVUsbUrbNext variable compared to 5.1.22/32.

Thanks for any thoughts,

Alexander Boettcher.

[0]
https://www.virtualbox.org/svn/vbox/trunk/src/VBox/Devices/USB/VUSBUrb.cpp
[1]
https://github.com/genodelabs/genode/commit/205c08bd9db9700f6a2629f97578e5fb9592fe94
[2] https://github.com/genodelabs/genode/issues/2612

-- 
Alexander Boettcher
Genode Labs

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