The patch titled
Subject: mm-check-against-orig_pte-for-finish_fault-fix
has been added to the -mm tree. Its filename is
mm-check-against-orig_pte-for-finish_fault-fix.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-check-against-orig_pte-for-finish_fault-fix.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-check-against-orig_pte-for-finish_fault-fix.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Peter Xu <peterx@xxxxxxxxxx>
Subject: mm-check-against-orig_pte-for-finish_fault-fix
fix crash reported by Marek
Link: https://lkml.kernel.org/r/Ylb9rXJyPm8/ao8f@xz-m1.local
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: Nadav Amit <nadav.amit@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/include/linux/mm_types.h~mm-check-against-orig_pte-for-finish_fault-fix
+++ a/include/linux/mm_types.h
@@ -814,6 +814,8 @@ typedef struct {
* @FAULT_FLAG_UNSHARE: The fault is an unsharing request to unshare (and mark
* exclusive) a possibly shared anonymous page that is
* mapped R/O.
+ * @FAULT_FLAG_ORIG_PTE_VALID: whether the fault has vmf->orig_pte cached.
+ * We should only access orig_pte if this flag set.
*
* About @FAULT_FLAG_ALLOW_RETRY and @FAULT_FLAG_TRIED: we can specify
* whether we would allow page faults to retry by specifying these two
@@ -850,6 +852,7 @@ enum fault_flag {
FAULT_FLAG_INSTRUCTION = 1 << 8,
FAULT_FLAG_INTERRUPTIBLE = 1 << 9,
FAULT_FLAG_UNSHARE = 1 << 10,
+ FAULT_FLAG_ORIG_PTE_VALID = 1 << 11,
};
#endif /* _LINUX_MM_TYPES_H */
--- a/mm/memory.c~mm-check-against-orig_pte-for-finish_fault-fix
+++ a/mm/memory.c
@@ -4194,6 +4194,15 @@ void do_set_pte(struct vm_fault *vmf, st
set_pte_at(vma->vm_mm, addr, vmf->pte, entry);
}
+static bool vmf_pte_changed(struct vm_fault *vmf)
+{
+ if (vmf->flags & FAULT_FLAG_ORIG_PTE_VALID) {
+ return !pte_same(*vmf->pte, vmf->orig_pte);
+ }
+
+ return !pte_none(*vmf->pte);
+}
+
/**
* finish_fault - finish page fault once we have prepared the page to fault
*
@@ -4252,7 +4261,7 @@ vm_fault_t finish_fault(struct vm_fault
vmf->address, &vmf->ptl);
ret = 0;
/* Re-check under ptl */
- if (likely(pte_same(*vmf->pte, vmf->orig_pte)))
+ if (likely(!vmf_pte_changed(vmf)))
do_set_pte(vmf, page, vmf->address);
else
ret = VM_FAULT_NOPAGE;
@@ -4720,13 +4729,7 @@ static vm_fault_t handle_pte_fault(struc
* concurrent faults and from rmap lookups.
*/
vmf->pte = NULL;
- /*
- * Always initialize orig_pte. This matches with below
- * code to have orig_pte to be the none pte if pte==NULL.
- * This makes the rest code to be always safe to reference
- * it, e.g. in finish_fault() we'll detect pte changes.
- */
- pte_clear(vmf->vma->vm_mm, vmf->address, &vmf->orig_pte);
+ vmf->flags &= ~FAULT_FLAG_ORIG_PTE_VALID;
} else {
/*
* If a huge pmd materialized under us just retry later. Use
@@ -4750,6 +4753,7 @@ static vm_fault_t handle_pte_fault(struc
*/
vmf->pte = pte_offset_map(vmf->pmd, vmf->address);
vmf->orig_pte = *vmf->pte;
+ vmf->flags |= FAULT_FLAG_ORIG_PTE_VALID;
/*
* some architectures can have larger ptes than wordsize,
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
mm-remove-stub-for-non_swap_entry.patch
mm-introduce-pte_marker-swap-entry.patch
mm-introduce-pte_marker-swap-entry-fix.patch
mm-teach-core-mm-about-pte-markers.patch
mm-check-against-orig_pte-for-finish_fault.patch
mm-check-against-orig_pte-for-finish_fault-fix.patch
mm-uffd-pte_marker_uffd_wp.patch
mm-uffd-pte_marker_uffd_wp-fix.patch
mm-shmem-take-care-of-uffdio_copy_mode_wp.patch
mm-shmem-handle-uffd-wp-special-pte-in-page-fault-handler.patch
mm-shmem-persist-uffd-wp-bit-across-zapping-for-file-backed.patch
mm-shmem-allow-uffd-wr-protect-none-pte-for-file-backed-mem.patch
mm-shmem-allows-file-back-mem-to-be-uffd-wr-protected-on-thps.patch
mm-shmem-handle-uffd-wp-during-fork.patch
mm-hugetlb-introduce-huge-pte-version-of-uffd-wp-helpers.patch
mm-hugetlb-hook-page-faults-for-uffd-write-protection.patch
mm-hugetlb-take-care-of-uffdio_copy_mode_wp.patch
mm-hugetlb-handle-uffdio_writeprotect.patch
mm-hugetlb-handle-pte-markers-in-page-faults.patch
mm-hugetlb-allow-uffd-wr-protect-none-ptes.patch
mm-hugetlb-only-drop-uffd-wp-special-pte-if-required.patch
mm-hugetlb-only-drop-uffd-wp-special-pte-if-required-fix.patch
mm-hugetlb-handle-uffd-wp-during-fork.patch
mm-khugepaged-dont-recycle-vma-pgtable-if-uffd-wp-registered.patch
mm-pagemap-recognize-uffd-wp-bit-for-shmem-hugetlbfs.patch
mm-uffd-enable-write-protection-for-shmem-hugetlbfs.patch
mm-enable-pte-markers-by-default.patch
selftests-uffd-enable-uffd-wp-for-shmem-hugetlbfs.patch
