This is a note to let you know that I've just added the patch titled
mm/userfaultfd: reset ptes when close() for wr-protected ones
to the 6.8-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-userfaultfd-reset-ptes-when-close-for-wr-protected-ones.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c88033efe9a391e72ba6b5df4b01d6e628f4e734 Mon Sep 17 00:00:00 2001
From: Peter Xu <peterx@xxxxxxxxxx>
Date: Mon, 22 Apr 2024 09:33:11 -0400
Subject: mm/userfaultfd: reset ptes when close() for wr-protected ones
From: Peter Xu <peterx@xxxxxxxxxx>
commit c88033efe9a391e72ba6b5df4b01d6e628f4e734 upstream.
Userfaultfd unregister includes a step to remove wr-protect bits from all
the relevant pgtable entries, but that only covered an explicit
UFFDIO_UNREGISTER ioctl, not a close() on the userfaultfd itself. Cover
that too. This fixes a WARN trace.
The only user visible side effect is the user can observe leftover
wr-protect bits even if the user close()ed on an userfaultfd when
releasing the last reference of it. However hopefully that should be
harmless, and nothing bad should happen even if so.
This change is now more important after the recent page-table-check
patch we merged in mm-unstable (446dd9ad37d0 ("mm/page_table_check:
support userfault wr-protect entries")), as we'll do sanity check on
uffd-wp bits without vma context. So it's better if we can 100%
guarantee no uffd-wp bit leftovers, to make sure each report will be
valid.
Link: https://lore.kernel.org/all/000000000000ca4df20616a0fe16@xxxxxxxxxx/
Fixes: f369b07c8614 ("mm/uffd: reset write protection when unregister with wp-mode")
Analyzed-by: David Hildenbrand <david@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20240422133311.2987675-1-peterx@xxxxxxxxxx
Reported-by: syzbot+d8426b591c36b21c750e@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Nadav Amit <nadav.amit@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/userfaultfd.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -925,6 +925,10 @@ static int userfaultfd_release(struct in
prev = vma;
continue;
}
+ /* Reset ptes for the whole vma range if wr-protected */
+ if (userfaultfd_wp(vma))
+ uffd_wp_range(vma, vma->vm_start,
+ vma->vm_end - vma->vm_start, false);
new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS;
vma = vma_modify_flags_uffd(&vmi, prev, vma, vma->vm_start,
vma->vm_end, new_flags,
Patches currently in stable-queue which might be from peterx@xxxxxxxxxx are
queue-6.8/mm-userfaultfd-reset-ptes-when-close-for-wr-protected-ones.patch
queue-6.8/fs-proc-task_mmu-fix-uffd-wp-confusion-in-pagemap_scan_pmd_entry.patch
queue-6.8/fs-proc-task_mmu-fix-loss-of-young-dirty-bits-during-pagemap-scan.patch
