Re: [PATCH 4.19 124/125] HID: hiddev: Fix slab-out-of-bounds write in hiddev_ioctl_usage()

On Tue, Sep 01, 2020 at 09:12:09PM +0200, Pavel Machek wrote:

Hi!

...

commit 25a097f5204675550afb879ee18238ca917cba7a upstream.

`uref->usage_index` is not always being properly checked, causing hiddev_ioctl_usage() to go out of bounds under some cases. Fix it.

Well, the code is quite confusig, but:

a) does HIDIOCGCOLLECTIONINDEX need same checking?

It's checked in the previous switch statement.

b) should we check this using some kind of _nospec() variant to prevent speculation attacks?

I don't think so. I wrote up an explanation earlier just because the code was so confusing.

https://lkml.org/lkml/2020/7/20/523

regards, dan carpenter