mm: Fix mremap not considering huge pmd devmap

commit 5bfea2d9b17f1034a68147a8b03b9789af5700f9 upstream.

The original code in mm/mremap.c checks huge pmd by:

		if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd)) {

However, a DAX mapped nvdimm is mapped as huge page (by default) but it
is not transparent huge page (_PAGE_PSE | PAGE_DEVMAP).  This commit
changes the condition to include the case.

This addresses CVE-2020-10757.

Fixes: 5c7fb56e5e3f ("mm, dax: dax-pmd vs thp-pmd vs hugetlbfs-pmd")
Cc: <>
Reported-by: Fan Yang <>
Signed-off-by: Fan Yang <>
Tested-by: Fan Yang <>
Tested-by: Dan Williams <>
Reviewed-by: Dan Williams <>
Acked-by: Kirill A. Shutemov <>
Signed-off-by: Linus Torvalds <>
Signed-off-by: Greg Kroah-Hartman <>

2 files changed