An issue was discovered in mm/mmap.c in the Linux kernel before 5.7.11. There is a race condition between certain expand functions (expand_downwards and expand_upwards) and page-table free operations from an munmap call, aka CID-246c320a8cfe.
www.openwall.com/lists/oss-security/2021/02/10/6
www.openwall.com/lists/oss-security/2021/02/19/8
bugs.chromium.org/p/project-zero/issues/detail?id=2056
cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.7.11
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=246c320a8cfe0b11d81a4af38fa9985ef0cc9a4c
security.netapp.com/advisory/ntap-20210115-0001/