userfaultfd: selftest
This test allocates two virtual areas and bounces the physical memory
across the two virtual areas using only userfaultfd.
This exposed a race condition in the refile of the userfault in
userfaultfd_read and an alignment issue with the address returned to
userland with THP enabled. It also allowed to test the interruption of
userfaults by signals (like running the testcase under gdb).
As expected no sign of memory corruption has ever materialized no
matter how I changed the stress test while developing it. The two bugs
had no impact on the safety and correctness of the memory being
tracked by userfaultfd. The fix for those two bugs was also
strightforward and required no design change of any sort.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
2 files changed
