+ mm-expose-abnormal-new_pte-during-move_ptes.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: expose abnormal new_pte during move_ptes
has been added to the -mm mm-unstable branch.  Its filename is
     mm-expose-abnormal-new_pte-during-move_ptes.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-expose-abnormal-new_pte-during-move_ptes.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Pu Lehui <pulehui@huawei.com>
Subject: mm: expose abnormal new_pte during move_ptes
Date: Thu, 29 May 2025 15:56:48 +0000

When executing move_ptes, the new_pte must be NULL, otherwise it will be
overwritten by the old_pte, and cause the abnormal new_pte to be leaked. 
In order to make this problem to be more explicit, let's add WARN_ON_ONCE
when new_pte is not NULL.

Link: https://lkml.kernel.org/r/20250529155650.4017699-3-pulehui@huaweicloud.com
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mremap.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/mremap.c~mm-expose-abnormal-new_pte-during-move_ptes
+++ a/mm/mremap.c
@@ -237,6 +237,8 @@ static int move_ptes(struct pagetable_mo
 
 	for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
 				   new_pte++, new_addr += PAGE_SIZE) {
+		WARN_ON_ONCE(!pte_none(*new_pte));
+
 		if (pte_none(ptep_get(old_pte)))
 			continue;
 
_

Patches currently in -mm which might be from pulehui@huawei.com are

mm-fix-uprobe-pte-be-overwritten-when-expanding-vma.patch
mm-expose-abnormal-new_pte-during-move_ptes.patch
selftests-mm-extract-read_sysfs-and-write_sysfs-into-vm_util.patch
selftests-mm-add-test-about-uprobe-pte-be-orphan-during-vma-merge.patch