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Howlett" Subject: [PATCH 6.6.y] mm/mempolicy: fix wrong mmap_read_unlock() in migrate_to_node() Date: Tue, 3 Mar 2026 11:12:45 +0100 Message-ID: <20260303101245.22290-1-david@kernel.org> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: A3F8040003 X-Stat-Signature: htrtsdinmojsgxor36nhphim6hdpofoh X-Rspam-User: X-HE-Tag: 1772532773-592494 X-HE-Meta: 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 I8nWe9BO 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The backport of commit 091c1dd2d4df ("mm/mempolicy: fix migrate_to_node() assuming there is at least one VMA in a MM") contains an error: migrate_to_node() does not lock the mmap_lock itself, that is handled by the caller instead. So let's drop the wrong mmap_read_unlock(). Fortunately, this path is very hard to hit in practice. Fixes: a13b2b9b0b0b ("mm/mempolicy: fix migrate_to_node() assuming there is at least one VMA in a MM") Reported-by: Li Ying Closes: https://lore.kernel.org/r/aaZgUNxAyKC2IwuG@casper.infradead.org Cc: Greg Kroah-Hartman Cc: Andrew Morton Cc: Matthew Wilcox Cc: Christoph Lameter Cc: Liam R. Howlett Cc: Signed-off-by: David Hildenbrand (Arm) --- mm/mempolicy.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 94c74c594d10..d8007e1c2690 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1071,10 +1071,8 @@ 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); + if (unlikely(!vma)) return 0; - } /* * This does not migrate the range, but isolates all pages that -- 2.43.0