summaryrefslogtreecommitdiff
path: root/mm
diff options
context:
space:
mode:
authorSuren Baghdasaryan <surenb@google.com>2024-01-11 17:39:35 -0800
committerAndrew Morton <akpm@linux-foundation.org>2024-01-12 15:20:49 -0800
commit5d4747a6cc8e78ce74742d557fc9b7697fcacc95 (patch)
tree8e459befcdcd7ff84cdb2e7a582198a46182ff12 /mm
parentaa8f91910bf5fb11dcd176e6efac2dbe2cecebea (diff)
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.c6
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) ||