The patch titled
Subject: mm/userfaultfd: fix uffd-wp handling for THP migration entries
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-userfaultfd-fix-uffd-wp-handling-for-thp-migration-entries.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-userfaultfd-fix-uffd-wp-handling-for-thp-migration-entries.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/userfaultfd: fix uffd-wp handling for THP migration entries
Date: Wed, 5 Apr 2023 18:02:35 +0200
Looks like what we fixed for hugetlb in commit 44f86392bdd1 ("mm/hugetlb:
fix uffd-wp handling for migration entries in
hugetlb_change_protection()") similarly applies to THP.
Setting/clearing uffd-wp on THP migration entries is not implemented
properly. Further, while removing migration PMDs considers the uffd-wp
bit, inserting migration PMDs does not consider the uffd-wp bit.
We have to set/clear independently of the migration entry type in
change_huge_pmd() and properly copy the uffd-wp bit in
set_pmd_migration_entry().
Verified using a simple reproducer that triggers migration of a THP, that
the set_pmd_migration_entry() no longer loses the uffd-wp bit.
Link: https://lkml.kernel.org/r/20230405160236.587705-2-david@xxxxxxxxxx
Fixes: f45ec5ff16a7 ("userfaultfd: wp: support swap and page migration")
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Cc: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
--- a/mm/huge_memory.c~mm-userfaultfd-fix-uffd-wp-handling-for-thp-migration-entries
+++ a/mm/huge_memory.c
@@ -1838,10 +1838,10 @@ int change_huge_pmd(struct mmu_gather *t
if (is_swap_pmd(*pmd)) {
swp_entry_t entry = pmd_to_swp_entry(*pmd);
struct page *page = pfn_swap_entry_to_page(entry);
+ pmd_t newpmd;
VM_BUG_ON(!is_pmd_migration_entry(*pmd));
if (is_writable_migration_entry(entry)) {
- pmd_t newpmd;
/*
* A protection check is difficult so
* just be safe and disable write
@@ -1855,8 +1855,16 @@ int change_huge_pmd(struct mmu_gather *t
newpmd = pmd_swp_mksoft_dirty(newpmd);
if (pmd_swp_uffd_wp(*pmd))
newpmd = pmd_swp_mkuffd_wp(newpmd);
- set_pmd_at(mm, addr, pmd, newpmd);
+ } else {
+ newpmd = *pmd;
}
+
+ if (uffd_wp)
+ newpmd = pmd_swp_mkuffd_wp(newpmd);
+ else if (uffd_wp_resolve)
+ newpmd = pmd_swp_clear_uffd_wp(newpmd);
+ if (!pmd_same(*pmd, newpmd))
+ set_pmd_at(mm, addr, pmd, newpmd);
goto unlock;
}
#endif
@@ -3251,6 +3259,8 @@ int set_pmd_migration_entry(struct page_
pmdswp = swp_entry_to_pmd(entry);
if (pmd_soft_dirty(pmdval))
pmdswp = pmd_swp_mksoft_dirty(pmdswp);
+ if (pmd_uffd_wp(pmdval))
+ pmdswp = pmd_swp_mkuffd_wp(pmdswp);
set_pmd_at(mm, address, pvmw->pmd, pmdswp);
page_remove_rmap(page, vma, true);
put_page(page);
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-userfaultfd-fix-uffd-wp-handling-for-thp-migration-entries.patch
m68k-mm-use-correct-bit-number-in-_page_swp_exclusive-comment.patch
mm-userfaultfd-dont-consider-uffd-wp-bit-of-writable-migration-entries.patch
