An issue was discovered in __split_huge_pmd in mm/huge_memory.c in the Linux kernel before 5.7.5. The copy-on-write implementation can grant unintended write access because of a race condition in a THP mapcount check, aka CID-c444eb564fb1.
https://security.netapp.com/advisory/ntap-20210108-0002/
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.7.5
https://bugs.chromium.org/p/project-zero/issues/detail?id=2045