linux-kernel - [PATCH 4.18 071/150] mm/gup_benchmark: fix unsigned comparison to zero in __gup_benchmark

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Date:   Fri,  2 Nov 2018 19:33:53 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, YueHaibing <yuehaibing@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.18 071/150] mm/gup_benchmark: fix unsigned comparison to zero in __gup_benchmark_ioctl

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 51896864579d5a3349740847083f4db5c6487164 ]

get_user_pages_fast() will return negative value if no pages were pinned,
then be converted to a unsigned, which is compared to zero, giving the
wrong result.

Link: http://lkml.kernel.org/r/20180921095015.26088-1-yuehaibing@huawei.com
Fixes: 09e35a4a1ca8 ("mm/gup_benchmark: handle gup failures")
Signed-off-by: YueHaibing <yuehaibing@...wei.com>
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 mm/gup_benchmark.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c
index 6a473709e9b6..7405c9d89d65 100644
--- a/mm/gup_benchmark.c
+++ b/mm/gup_benchmark.c
@@ -19,7 +19,8 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
 		struct gup_benchmark *gup)
 {
 	ktime_t start_time, end_time;
-	unsigned long i, nr, nr_pages, addr, next;
+	unsigned long i, nr_pages, addr, next;
+	int nr;
 	struct page **pages;
 
 	nr_pages = gup->size / PAGE_SIZE;
-- 
2.17.1