The quilt patch titled
Subject: mm: add early FAULT_FLAG_WRITE consistency checks
has been removed from the -mm tree. Its filename was
mm-add-early-fault_flag_write-consistency-checks.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm: add early FAULT_FLAG_WRITE consistency checks
Date: Wed, 16 Nov 2022 11:26:44 +0100
Let's catch abuse of FAULT_FLAG_WRITE early, such that we don't have to
care in all other handlers and might get "surprises" if we forget to do
so.
Write faults without VM_MAYWRITE don't make any sense, and our
maybe_mkwrite() logic could have hidden such abuse for now.
Write faults without VM_WRITE on something that is not a COW mapping is
similarly broken, and e.g., do_wp_page() could end up placing an
anonymous page into a shared mapping, which would be bad.
This is a preparation for reliable R/O long-term pinning of pages in
private mappings, whereby we want to make sure that we will never break
COW in a read-only private mapping.
Link: https://lkml.kernel.org/r/20221116102659.70287-6-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/mm/memory.c~mm-add-early-fault_flag_write-consistency-checks
+++ a/mm/memory.c
@@ -5170,6 +5170,14 @@ static vm_fault_t sanitize_fault_flags(s
*/
if (!is_cow_mapping(vma->vm_flags))
*flags &= ~FAULT_FLAG_UNSHARE;
+ } else if (*flags & FAULT_FLAG_WRITE) {
+ /* Write faults on read-only mappings are impossible ... */
+ if (WARN_ON_ONCE(!(vma->vm_flags & VM_MAYWRITE)))
+ return VM_FAULT_SIGSEGV;
+ /* ... and FOLL_FORCE only applies to COW mappings. */
+ if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE) &&
+ !is_cow_mapping(vma->vm_flags)))
+ return VM_FAULT_SIGSEGV;
}
return 0;
}
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
selftests-vm-add-ksm-unmerge-tests.patch
mm-pagewalk-dont-trigger-test_walk-in-walk_page_vma.patch
selftests-vm-add-test-to-measure-madv_unmergeable-performance.patch
mm-ksm-simplify-break_ksm-to-not-rely-on-vm_fault_write.patch
mm-remove-vm_fault_write.patch
mm-ksm-fix-ksm-cow-breaking-with-userfaultfd-wp-via-fault_flag_unshare.patch
mm-pagewalk-add-walk_page_range_vma.patch
mm-ksm-convert-break_ksm-to-use-walk_page_range_vma.patch
mm-gup-remove-foll_migration.patch
