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| author | Suren Baghdasaryan <surenb@google.com> | 2024-01-11 17:39:35 -0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-01-12 15:20:49 -0800 |
| commit | 5d4747a6cc8e78ce74742d557fc9b7697fcacc95 (patch) | |
| tree | 8e459befcdcd7ff84cdb2e7a582198a46182ff12 /mm | |
| parent | aa8f91910bf5fb11dcd176e6efac2dbe2cecebea (diff) | |
| download | linux-5d4747a6cc8e78ce74742d557fc9b7697fcacc95.tar.gz linux-5d4747a6cc8e78ce74742d557fc9b7697fcacc95.tar.bz2 linux-5d4747a6cc8e78ce74742d557fc9b7697fcacc95.zip | |
userfaultfd: avoid huge_zero_page in UFFDIO_MOVE
While testing UFFDIO_MOVE ioctl, syzbot triggered VM_BUG_ON_PAGE caused by
a call to PageAnonExclusive() with a huge_zero_page as a parameter.
UFFDIO_MOVE does not yet handle zeropages and returns EBUSY when one is
encountered. Add an early huge_zero_page check in the PMD move path to
avoid this situation.
Link: https://lkml.kernel.org/r/20240112013935.1474648-1-surenb@google.com
Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI")
Reported-by: syzbot+705209281e36404998f6@syzkaller.appspotmail.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/userfaultfd.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 216ab4c8621f..20e3b0d9cf7e 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1393,6 +1393,12 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, err = -ENOENT; break; } + /* Avoid moving zeropages for now */ + if (is_huge_zero_pmd(*src_pmd)) { + spin_unlock(ptl); + err = -EBUSY; + break; + } /* Check if we can move the pmd without splitting it. */ if (move_splits_huge_pmd(dst_addr, src_addr, src_start + len) || |