Description: mm: Fix mremap not considering huge pmd devmap
References:
 https://lore.kernel.org/lkml/A82D1BB5-D868-489A-BFED-9FCE71649A46@sjtu.edu.cn/
 https://www.openwall.com/lists/oss-security/2020/06/04/4
Notes:
 carnil> Introduced in 5c7fb56e5e3f ("mm, dax: dax-pmd vs thp-pmd vs
 carnil> hugetlbfs-pmd") in 4.5-rc1
Bugs:
upstream: released (5.8-rc1) [5bfea2d9b17f1034a68147a8b03b9789af5700f9]
4.19-upstream-stable: released (4.19.127) [78385480fd6572a83e7541e37658d9a7de6dc9b1]
4.9-upstream-stable: released (4.9.227) [c915cffda0a4329ee454646138fe2b11c5ba3cd6]
3.16-upstream-stable: N/A "Vulnerable code introduced later"
sid: released (5.6.14-2) [bugfix/all/mm-Fix-mremap-not-considering-huge-pmd-devmap.patch]
4.19-buster-security: released (4.19.118-2+deb10u1) [bugfix/all/mm-Fix-mremap-not-considering-huge-pmd-devmap.patch]
4.9-stretch-security: released (4.9.210-1+deb9u1) [bugfix/all/mm-Fix-mremap-not-considering-huge-pmd-devmap.patch]
3.16-jessie-security: N/A "Vulnerable code introduced later"