On Wed, May 5, 2021 at 2:42 PM Jiri Kosina [off-list ref] wrote:

On Sun, 25 Apr 2021, Anirudh Rayabharam wrote:

quoted

In hid_submit_ctrl(), the way of calculating the report length doesn't
take into account that report->size can be zero. When running the
syzkaller reproducer, a report of size 0 causes hid_submit_ctrl) to
calculate transfer_buffer_length as 16384. When this urb is passed to
the usb core layer, KMSAN reports an info leak of 16384 bytes.

To fix this, first modify hid_report_len() to account for the zero
report size case by using DIV_ROUND_UP for the division. Then, call it
from hid_submit_ctrl().

Reported-by: syzbot+7c2bb71996f95a82524c@syzkaller.appspotmail.com
Signed-off-by: Anirudh Rayabharam <redacted>

Benjamin, could you please run this one through your regression testing
machinery before we send it upstream?

I don't have a reproducer like syzbot has for the exact bug here, as I
am relying on one real USB device to check if usbhid is not too
broken.
However, the test suite should catch if there is an error implied by
the hid_report_len() change.

Anyway, I manually started the job and will report when it is done.

Cheers,
Benjamin