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cpuset_set{affinity,domain}: do not allow empty masks

Authored by kevans on Dec 8 2020, 2:29 PM.



cpuset_modify() would not currently catch this, because it only checks that the new mask is a subset of the root set and circumvents the EDEADLK check in cpuset_testupdate().

This change both directly validates the mask coming in since we can trivially detect an empty mask, and it updates cpuset_testupdate to catch stuff like this going forward by always ensuring we don't end up with an empty mask.

The check_mask argument has been renamed because the 'check' verbiage does not imply to me that it's actually doing a different operation. We're either augmenting the existing mask, or we are replacing it entirely.

Reported by:

Test Plan

I could not reproduce this one from syzbot's repro, but it's clear that it is a problem

Diff Detail

rS FreeBSD src repository - subversion
Automatic diff as part of commit; lint not applicable.
Automatic diff as part of commit; unit tests not applicable.