The patch titled
Subject: mm/userfaultfd: UFFDIO_MOVE implementation should use ptep_get()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-userfaultfd-uffdio_move-implementation-should-use-ptep_get.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-userfaultfd-uffdio_move-implementation-should-use-ptep_get.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: Ryan Roberts <ryan.roberts@xxxxxxx>
Subject: mm/userfaultfd: UFFDIO_MOVE implementation should use ptep_get()
Date: Tue, 23 Jan 2024 14:17:55 +0000
Commit c33c794828f2 ("mm: ptep_get() conversion") converted all (non-arch)
call sites to use ptep_get() instead of doing a direct dereference of the
pte. Full rationale can be found in that commit's log.
Since then, UFFDIO_MOVE has been implemented which does 7 direct pte
dereferences. Let's fix those up to use ptep_get().
I've asserted in the past that there is no reliable automated mechanism to
catch these; I'm relying on a combination of Coccinelle (which throws up a
lot of false positives) and some compiler magic to force a compiler error
on dereference. But given the frequency with which new issues are coming
up, I'll add it to my todo list to try to find an automated solution.
Link: https://lkml.kernel.org/r/20240123141755.3836179-1-ryan.roberts@xxxxxxx
Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI")
Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
Reviewed-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/userfaultfd.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
--- a/mm/userfaultfd.c~mm-userfaultfd-uffdio_move-implementation-should-use-ptep_get
+++ a/mm/userfaultfd.c
@@ -902,8 +902,8 @@ static int move_present_pte(struct mm_st
double_pt_lock(dst_ptl, src_ptl);
- if (!pte_same(*src_pte, orig_src_pte) ||
- !pte_same(*dst_pte, orig_dst_pte)) {
+ if (!pte_same(ptep_get(src_pte), orig_src_pte) ||
+ !pte_same(ptep_get(dst_pte), orig_dst_pte)) {
err = -EAGAIN;
goto out;
}
@@ -946,8 +946,8 @@ static int move_swap_pte(struct mm_struc
double_pt_lock(dst_ptl, src_ptl);
- if (!pte_same(*src_pte, orig_src_pte) ||
- !pte_same(*dst_pte, orig_dst_pte)) {
+ if (!pte_same(ptep_get(src_pte), orig_src_pte) ||
+ !pte_same(ptep_get(dst_pte), orig_dst_pte)) {
double_pt_unlock(dst_ptl, src_ptl);
return -EAGAIN;
}
@@ -1016,7 +1016,7 @@ retry:
}
spin_lock(dst_ptl);
- orig_dst_pte = *dst_pte;
+ orig_dst_pte = ptep_get(dst_pte);
spin_unlock(dst_ptl);
if (!pte_none(orig_dst_pte)) {
err = -EEXIST;
@@ -1024,7 +1024,7 @@ retry:
}
spin_lock(src_ptl);
- orig_src_pte = *src_pte;
+ orig_src_pte = ptep_get(src_pte);
spin_unlock(src_ptl);
if (pte_none(orig_src_pte)) {
if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES))
@@ -1054,7 +1054,7 @@ retry:
* page isn't freed under us
*/
spin_lock(src_ptl);
- if (!pte_same(orig_src_pte, *src_pte)) {
+ if (!pte_same(orig_src_pte, ptep_get(src_pte))) {
spin_unlock(src_ptl);
err = -EAGAIN;
goto out;
_
Patches currently in -mm which might be from ryan.roberts@xxxxxxx are
selftests-mm-ksm_tests-should-only-madv_hugepage-valid-memory.patch
mm-thp_get_unmapped_area-must-honour-topdown-preference.patch
mm-userfaultfd-uffdio_move-implementation-should-use-ptep_get.patch
tools-mm-add-thpmaps-script-to-dump-thp-usage-info.patch
