Description: mm/mmap.c: close race between munmap() and expand_upwards()/downwards()
References:
 https://bugs.chromium.org/p/project-zero/issues/detail?id=2056
Notes:
Bugs:
upstream: released (5.8-rc7) [246c320a8cfe0b11d81a4af38fa9985ef0cc9a4c]
4.19-upstream-stable: N/A "Vulnerable code introduced later"
4.9-upstream-stable: N/A "Vulnerable code introduced later"
sid: released (5.7.17-1)
4.19-buster-security: N/A "Vulnerable code introduced later"
4.9-stretch-security: N/A "Vulnerable code introduced later"