linux-kernel - [PATCH] mm/huge_memory: Return from zap_huge_pmd after WARN

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Date:   Fri, 15 Jul 2022 09:22:38 +0000
From:   Zhou Guanghui <zhouguanghui1@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <zhouguanghui1@...wei.com>
Subject: [PATCH] mm/huge_memory: Return from zap_huge_pmd after WARN_ONCE.

After WARN_ONCE is processed, the subsequent page judgment results
in NULL pointer access. It is more reasonable to return from the
function here.

Signed-off-by: Zhou Guanghui <zhouguanghui1@...wei.com>
---
 mm/huge_memory.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 834f288b3769..7f5ccca6792a 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1601,8 +1601,11 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 			entry = pmd_to_swp_entry(orig_pmd);
 			page = pfn_swap_entry_to_page(entry);
 			flush_needed = 0;
-		} else
+		} else {
+			spin_unlock(ptl);
 			WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
+			return 1;
+		}
 
 		if (PageAnon(page)) {
 			zap_deposited_table(tlb->mm, pmd);
-- 
2.17.1