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| author | Peter Xu <peterx@redhat.com> | 2024-03-13 17:31:07 -0400 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-03-26 11:07:19 -0700 |
| commit | f8572367eaff6739e3bc238ba93b86cd7881c0ff (patch) | |
| tree | b95652c2e8edb7be298c8b7f42e86acb87b51466 | |
| parent | 4cece764965020c22cff7665b18a012006359095 (diff) | |
| download | linux-f8572367eaff6739e3bc238ba93b86cd7881c0ff.tar.gz | |
mm/memory: fix missing pte marker for !page on pte zaps
Commit 0cf18e839f64 of large folio zap work broke uffd-wp. Now mm's uffd
unit test "wp-unpopulated" will trigger this WARN_ON_ONCE().
The WARN_ON_ONCE() asserts that an VMA cannot be registered with
userfaultfd-wp if it contains a !normal page, but it's actually possible.
One example is an anonymous vma, register with uffd-wp, read anything will
install a zero page. Then when zap on it, this should trigger.
What's more, removing that WARN_ON_ONCE may not be enough either, because
we should also not rely on "whether it's a normal page" to decide whether
pte marker is needed. For example, one can register wr-protect over some
DAX regions to track writes when UFFD_FEATURE_WP_ASYNC enabled, in which
case it can have page==NULL for a devmap but we may want to keep the
marker around.
Link: https://lkml.kernel.org/r/20240313213107.235067-1-peterx@redhat.com
Fixes: 0cf18e839f64 ("mm/memory: handle !page case in zap_present_pte() separately")
Signed-off-by: Peter Xu <peterx@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | mm/memory.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/mm/memory.c b/mm/memory.c index f2bc6dd15eb830..904f70b994985a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1536,7 +1536,9 @@ static inline int zap_present_ptes(struct mmu_gather *tlb, ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); arch_check_zapped_pte(vma, ptent); tlb_remove_tlb_entry(tlb, pte, addr); - VM_WARN_ON_ONCE(userfaultfd_wp(vma)); + if (userfaultfd_pte_wp(vma, ptent)) + zap_install_uffd_wp_if_needed(vma, addr, pte, 1, + details, ptent); ksm_might_unmap_zero_page(mm, ptent); return 1; } |