diff options
| author | Suren Baghdasaryan <surenb@google.com> | 2025-08-06 15:00:22 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-08-20 18:30:54 +0200 |
| commit | bb81c18dbd42650c844e160cafa7cbb20243a96a (patch) | |
| tree | 91ae111a5b294f9affa83e46e165866b15f48af4 | |
| parent | 579c5488fe6e31097482cdc15ca2e4ae53b5c0b6 (diff) | |
userfaultfd: fix a crash in UFFDIO_MOVE when PMD is a migration entry
commit aba6faec0103ed8f169be8dce2ead41fcb689446 upstream.
When UFFDIO_MOVE encounters a migration PMD entry, it proceeds with
obtaining a folio and accessing it even though the entry is swp_entry_t.
Add the missing check and let split_huge_pmd() handle migration entries.
While at it also remove unnecessary folio check.
[surenb@google.com: remove extra folio check, per David]
Link: https://lkml.kernel.org/r/20250807200418.1963585-1-surenb@google.com
Link: https://lkml.kernel.org/r/20250806220022.926763-1-surenb@google.com
Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reported-by: syzbot+b446dbe27035ef6bd6c2@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68794b5c.a70a0220.693ce.0050.GAE@google.com/
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | mm/userfaultfd.c | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 2646b75163d5..8b0f2fbd6a75 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1800,13 +1800,16 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start, /* Check if we can move the pmd without splitting it. */ if (move_splits_huge_pmd(dst_addr, src_addr, src_start + len) || !pmd_none(dst_pmdval)) { - struct folio *folio = pmd_folio(*src_pmd); - - if (!folio || (!is_huge_zero_folio(folio) && - !PageAnonExclusive(&folio->page))) { - spin_unlock(ptl); - err = -EBUSY; - break; + /* Can be a migration entry */ + if (pmd_present(*src_pmd)) { + struct folio *folio = pmd_folio(*src_pmd); + + if (!is_huge_zero_folio(folio) && + !PageAnonExclusive(&folio->page)) { + spin_unlock(ptl); + err = -EBUSY; + break; + } } spin_unlock(ptl); |