FAILED: patch "[PATCH] mm/mremap: use pudp_huge_get_and_clear() when moving huge PUDs" failed to apply to 5.15-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 5.15-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 <stable@vger.kernel.org>.

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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x b4417d08034a7b4a3083e0e2d95429d4542524f2
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109202333-failed-5.15-b4417d08034a@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Thanks,
Sasha

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

From b4417d08034a7b4a3083e0e2d95429d4542524f2 Mon Sep 17 00:00:00 2001
From: "David Hildenbrand (Arm)" <david@kernel.org>
Date: Sat, 31 Oct 2026 10:39:59 +0100
Subject: [PATCH] mm/mremap: use pudp_huge_get_and_clear() when moving huge
 PUDs

move_huge_pud() reads the old PUD and clears it in separate operations.
Hardware accessed or dirty updates between those operations can be lost
when the saved entry is installed at the new address.

The raw pud_clear() also bypasses page_table_check_pud_clear(), while
set_pud_at() accounts for the destination mapping. This leaves the
checker counts unbalanced for mappings tracked by page table checking.

To fix it, simply use pudp_huge_get_and_clear().

Fixes: 7d846db7d0e2 ("mm/mremap: convert huge PUD move to separate helper")
Cc: stable@vger.kernel.org
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Link: https://patch.msgid.link/20261031-fixes_core-v3-30-d6437171ecc3@kernel.org
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 mm/mremap.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/mremap.c b/mm/mremap.c
index 0d06d7f37f19a..16e736c72d9cb 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -509,8 +509,7 @@ static bool move_huge_pud(struct pagetable_move_control *pmc,
 		spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
 
 	/* Clear the pud */
-	pud = *old_pud;
-	pud_clear(old_pud);
+	pud = pudp_huge_get_and_clear(mm, pmc->old_addr, old_pud);
 
 	VM_BUG_ON(!pud_none(*new_pud));
 
-- 
2.53.0