linux-kernel - [PATCH 4/5] mm: gup: fix potential pgmap refcnt leak in __gup_device

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Message-ID: <20210807093620.21347-5-linmiaohe@huawei.com>
Date:   Sat, 7 Aug 2021 17:36:19 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <imbrenda@...ux.ibm.com>, <kirill.shutemov@...ux.intel.com>,
        <jack@...e.cz>, <jhubbard@...dia.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <linmiaohe@...wei.com>
Subject: [PATCH 4/5] mm: gup: fix potential pgmap refcnt leak in __gup_device_huge()

When failed to try_grab_page, put_dev_pagemap() is missed. So pgmap
refcnt will leak in this case. Also we remove the check for pgmap
against NULL as it's also checked inside the put_dev_pagemap().

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
Fixes: 3faa52c03f44 ("mm/gup: track FOLL_PIN pages")
---
 mm/gup.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index d7e4507de6b1..8c89e614d4aa 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2253,14 +2253,14 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
 		pages[*nr] = page;
 		if (unlikely(!try_grab_page(page, flags))) {
 			undo_dev_pagemap(nr, nr_start, flags, pages);
+			put_dev_pagemap(pgmap);
 			return 0;
 		}
 		(*nr)++;
 		pfn++;
 	} while (addr += PAGE_SIZE, addr != end);
 
-	if (pgmap)
-		put_dev_pagemap(pgmap);
+	put_dev_pagemap(pgmap);
 	return 1;
 }
 
-- 
2.23.0