This is a note to let you know that I've just added the patch titled
mm/swap: fix pte_same_as_swp() not removing uffd-wp bit when compare
to the 5.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-swap-fix-pte_same_as_swp-not-removing-uffd-wp-bit-when-compare.patch
and it can be found in the queue-5.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 099dd6878b9b12d6bbfa6bf29ce0c8ddd38f6901 Mon Sep 17 00:00:00 2001
From: Peter Xu <peterx@xxxxxxxxxx>
Date: Tue, 15 Jun 2021 18:23:16 -0700
Subject: mm/swap: fix pte_same_as_swp() not removing uffd-wp bit when compare
From: Peter Xu <peterx@xxxxxxxxxx>
commit 099dd6878b9b12d6bbfa6bf29ce0c8ddd38f6901 upstream.
I found it by pure code review, that pte_same_as_swp() of unuse_vma()
didn't take uffd-wp bit into account when comparing ptes.
pte_same_as_swp() returning false negative could cause failure to
swapoff swap ptes that was wr-protected by userfaultfd.
Link: https://lkml.kernel.org/r/20210603180546.9083-1-peterx@xxxxxxxxxx
Fixes: f45ec5ff16a7 ("userfaultfd: wp: support swap and page migration")
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [5.7+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/swapops.h | 15 +++++++++++----
mm/swapfile.c | 2 +-
2 files changed, 12 insertions(+), 5 deletions(-)
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -23,6 +23,16 @@
#define SWP_TYPE_SHIFT (BITS_PER_XA_VALUE - MAX_SWAPFILES_SHIFT)
#define SWP_OFFSET_MASK ((1UL << SWP_TYPE_SHIFT) - 1)
+/* Clear all flags but only keep swp_entry_t related information */
+static inline pte_t pte_swp_clear_flags(pte_t pte)
+{
+ if (pte_swp_soft_dirty(pte))
+ pte = pte_swp_clear_soft_dirty(pte);
+ if (pte_swp_uffd_wp(pte))
+ pte = pte_swp_clear_uffd_wp(pte);
+ return pte;
+}
+
/*
* Store a type+offset into a swp_entry_t in an arch-independent format
*/
@@ -66,10 +76,7 @@ static inline swp_entry_t pte_to_swp_ent
{
swp_entry_t arch_entry;
- if (pte_swp_soft_dirty(pte))
- pte = pte_swp_clear_soft_dirty(pte);
- if (pte_swp_uffd_wp(pte))
- pte = pte_swp_clear_uffd_wp(pte);
+ pte = pte_swp_clear_flags(pte);
arch_entry = __pte_to_swp_entry(pte);
return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
}
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1900,7 +1900,7 @@ unsigned int count_swap_pages(int type,
static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
{
- return pte_same(pte_swp_clear_soft_dirty(pte), swp_pte);
+ return pte_same(pte_swp_clear_flags(pte), swp_pte);
}
/*
Patches currently in stable-queue which might be from peterx@xxxxxxxxxx are
queue-5.12/mm-swap-fix-pte_same_as_swp-not-removing-uffd-wp-bit-when-compare.patch
queue-5.12/mm-hugetlb-expand-restore_reserve_on_error-functionality.patch
queue-5.12/mm-relocate-write_protect_seq-in-struct-mm_struct.patch
