Commit 92cde6a9 authored by Peter Xu's avatar Peter Xu Committed by Liu Shixin
Browse files

mm/userfaultfd: reset ptes when close() for wr-protected ones 

stable inclusion
from stable-v6.6.31
commit 377f3a9a3d032a52325a5b110379a25dd1ab1931
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9UOJV
CVE: CVE-2024-36881

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=377f3a9a3d032a52325a5b110379a25dd1ab1931

--------------------------------

commit c88033efe9a391e72ba6b5df4b01d6e628f4e734 upstream.

Userfaultfd unregister includes a step to remove wr-protect bits from all
the relevant pgtable entries, but that only covered an explicit
UFFDIO_UNREGISTER ioctl, not a close() on the userfaultfd itself.  Cover
that too.  This fixes a WARN trace.

The only user visible side effect is the user can observe leftover
wr-protect bits even if the user close()ed on an userfaultfd when
releasing the last reference of it.  However hopefully that should be
harmless, and nothing bad should happen even if so.

This change is now more important after the recent page-table-check
patch we merged in mm-unstable (446dd9ad37d0 ("mm/page_table_check:
support userfault wr-protect entries")), as we'll do sanity check on
uffd-wp bits without vma context.  So it's better if we can 100%
guarantee no uffd-wp bit leftovers, to make sure each report will be
valid.

Link: https://lore.kernel.org/all/000000000000ca4df20616a0fe16@google.com/


Fixes: f369b07c ("mm/uffd: reset write protection when unregister with wp-mode")
Analyzed-by: default avatarDavid Hildenbrand <david@redhat.com>
Link: https://lkml.kernel.org/r/20240422133311.2987675-1-peterx@redhat.com


Reported-by: default avatar <syzbot+d8426b591c36b21c750e@syzkaller.appspotmail.com>
Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Conflicts:
	fs/userfaultfd.c
[ Context conflicts due to commit b54b55c3 ]
Signed-off-by: default avatarLiu Shixin <liushixin2@huawei.com>
parent dc3e4805

fs/userfaultfd.c

+4 −0
Original line number Diff line number Diff line
@@ -939,6 +939,10 @@ static int userfaultfd_release(struct inode *inode, struct file *file) 
			prev = vma;

			continue;

		}

		/* Reset ptes for the whole vma range if wr-protected */

		if (userfaultfd_wp(vma))

			uffd_wp_range(vma, vma->vm_start,

				      vma->vm_end - vma->vm_start, false);

		new_flags = vma->vm_flags & ~(__VM_UFFD_FLAGS | VM_USWAP);

		prev = vma_merge(&vmi, mm, prev, vma->vm_start, vma->vm_end,

				 new_flags, vma->anon_vma,