[BUG] mm/mempolicy: possible double-unlock in migrate_to_node() on 6.6

["liying3@sungrowpower.com" <liying3@sungrowpower.com>]

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Hi Andrew,

I found that a fix is required for this submission in branch 6.6.
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a13b2b9b0b0b04612c7d81e3b3dfb485c5f7abc3 

Regarding the difference between branches 6.6 and 6.12, in branch 6.6, mmap_read_lock() and mmap_read_unlock() are called outside the migrate_to_node() function. 
Therefore, mmap_read_unlock(mm) should not be invoked inside migrate_to_node(); otherwise, it would result in a double unlock of the mm.
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 54f1b78d1b2c0f..94c74c594d102a 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1071,6 +1071,10 @@ static long migrate_to_node(struct mm_struct *mm, int source, int dest,
VM_BUG_ON(!(flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)));
vma = find_vma(mm, 0);
+ if (unlikely(!vma)) {
+ mmap_read_unlock(mm); // this line should be deleted
+ return 0;
+ }
/*
* This does not migrate the range, but isolates all pages that



Best Regards,
Li Ying , Light Storage Group.  Senior Embedded Software Engineer
Tel: -； Fax: -
Mobile: +86-15651963981
liying3@sungrowpower.com 
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SUNGROW POWER SUPPLY Co., Ltd. 
Add: No.1699 Xiyou Rd., New & High Technology Industrial Development Zone, Hefei, P. R. China., 230088

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