linux-kernel - [PATCH] mm/mempolicy: fix potential mpol_new leak in shared_policy

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Message-ID: <20220311093624.39546-1-linmiaohe@huawei.com>
Date:   Fri, 11 Mar 2022 17:36:24 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <kosaki.motohiro@...fujitsu.com>, <mgorman@...e.de>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH] mm/mempolicy: fix potential mpol_new leak in shared_policy_replace

If mpol_new is allocated but not used in restart loop, mpol_new will be
freed via mpol_put before returning to the caller. But refcnt is not
initialized yet, so mpol_put could not do the right things and might
leak the unused mpol_new.

Fixes: 42288fe366c4 ("mm: mempolicy: Convert shared_policy mutex to spinlock")
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/mempolicy.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 34d2b29c96ad..f19f19d3558b 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2733,6 +2733,7 @@ static int shared_policy_replace(struct shared_policy *sp, unsigned long start,
 	mpol_new = kmem_cache_alloc(policy_cache, GFP_KERNEL);
 	if (!mpol_new)
 		goto err_out;
+	refcount_set(&mpol_new->refcnt, 1);
 	goto restart;
 }
 
-- 
2.23.0