New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Order of operations error and missing exception handling #22

Open

ChopperCharles opened this issue Jul 24, 2019 · 0 comments

ChopperCharles commented Jul 24, 2019

In NDisDriver.c, line 1531 the following code will always evaluate to 0:

tag_us = (qinfo.TagHeader.UserPriority & 0x07 << 13) |
(qinfo.TagHeader.CanonicalFormatId & 0x01 << 12) |
(qinfo.TagHeader.VlanId & 0x0FFF);

This is because the shift operations take precedence over the and operations. To correct this, add parenthesis as such:

tag_us = ((qinfo.TagHeader.UserPriority & 0x07) << 13) |
((qinfo.TagHeader.CanonicalFormatId & 0x01) << 12) |
(qinfo.TagHeader.VlanId & 0x0FFF);

In addition, anywhere there is a ProbeForRead or ProbeForWrite, these should be surrounded by a _try / _except block (and so should any additional access to the buffers). See https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/content/wdm/nf-wdm-probeforread for more information.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment