linux-kernel - [PATCH AUTOSEL 5.1 021/186] mm/cma_debug.c: fix the break condition in cma_maxchunk

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Date:   Sat,  1 Jun 2019 09:13:57 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Yue Hu <huyue2@...ong.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>, Joe Perches <joe@...ches.com>,
        David Rientjes <rientjes@...gle.com>,
        Dmitry Safonov <d.safonov@...tner.samsung.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>, linux-mm@...ck.org
Subject: [PATCH AUTOSEL 5.1 021/186] mm/cma_debug.c: fix the break condition in cma_maxchunk_get()

From: Yue Hu <huyue2@...ong.com>

[ Upstream commit f0fd50504a54f5548eb666dc16ddf8394e44e4b7 ]

If not find zero bit in find_next_zero_bit(), it will return the size
parameter passed in, so the start bit should be compared with bitmap_maxno
rather than cma->count.  Although getting maxchunk is working fine due to
zero value of order_per_bit currently, the operation will be stuck if
order_per_bit is set as non-zero.

Link: http://lkml.kernel.org/r/20190319092734.276-1-zbestahu@gmail.com
Signed-off-by: Yue Hu <huyue2@...ong.com>
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Joe Perches <joe@...ches.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Dmitry Safonov <d.safonov@...tner.samsung.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 mm/cma_debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/cma_debug.c b/mm/cma_debug.c
index 8d7b2fd522259..a7dd9e8e10d5d 100644
--- a/mm/cma_debug.c
+++ b/mm/cma_debug.c
@@ -56,7 +56,7 @@ static int cma_maxchunk_get(void *data, u64 *val)
 	mutex_lock(&cma->lock);
 	for (;;) {
 		start = find_next_zero_bit(cma->bitmap, bitmap_maxno, end);
-		if (start >= cma->count)
+		if (start >= bitmap_maxno)
 			break;
 		end = find_next_bit(cma->bitmap, bitmap_maxno, start);
 		maxchunk = max(end - start, maxchunk);
-- 
2.20.1