From: Peter Xu peterx@redhat.com

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=...

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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: f369b07c8614 ("mm/uffd: reset write protection when unregister with wp-mode") Analyzed-by: David Hildenbrand david@redhat.com Link: https://lkml.kernel.org/r/20240422133311.2987675-1-peterx@redhat.com Reported-by: syzbot+d8426b591c36b21c750e@syzkaller.appspotmail.com Signed-off-by: Peter Xu peterx@redhat.com Reviewed-by: David Hildenbrand david@redhat.com Cc: Nadav Amit nadav.amit@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Conflicts: fs/userfaultfd.c [ Context conflicts due to commit b54b55c3305c ] Signed-off-by: Liu Shixin liushixin2@huawei.com --- fs/userfaultfd.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 232f12b4bc0a..e7cb9d70cad9 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -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,