FAILED: patch "[PATCH] mm/userfaultfd: reset ptes when close() for wr-protected ones" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x c88033efe9a391e72ba6b5df4b01d6e628f4e734
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024051304-turkey-underfed-40fe@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

c88033efe9a3 ("mm/userfaultfd: reset ptes when close() for wr-protected ones")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c88033efe9a391e72ba6b5df4b01d6e628f4e734 Mon Sep 17 00:00:00 2001
From: Peter Xu <[email protected]>
Date: Mon, 22 Apr 2024 09:33:11 -0400
Subject: [PATCH] mm/userfaultfd: reset ptes when close() for wr-protected ones

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.

index 60dcfafdc11a..292f5fd50104 100644
@@ -895,6 +895,10 @@ 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;
 		vma = vma_modify_flags_uffd(&vmi, prev, vma, vma->vm_start,
 					    vma->vm_end, new_flags,