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From:   Jianqun Xu <jay.xu@rock-chips.com>
To:     akpm@linux-foundation.org
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Jianqun Xu <jay.xu@rock-chips.com>
Subject: [PATCH] mm/cma: fix NULL pointer dereference when cma could not be activated
Date:   Mon, 15 Jun 2020 09:01:23 +0800
Message-Id: <20200615010123.15596-1-jay.xu@rock-chips.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In some case the cma area could not be activated, but the cma_alloc be
used under this case, then the kernel will crash caused by NULL pointer
dereference.

Add bitmap valid check in cma_alloc to avoid this issue.

Signed-off-by: Jianqun Xu <jay.xu@rock-chips.com>
---
 mm/cma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/cma.c b/mm/cma.c
index 0463ad2ce06b..488496fa2972 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -425,7 +425,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 	struct page *page = NULL;
 	int ret = -ENOMEM;
 
-	if (!cma || !cma->count)
+	if (!cma || !cma->count || !cma->bitmap)
 		return NULL;
 
 	pr_debug("%s(cma %p, count %zu, align %d)\n", __func__, (void *)cma,
-- 
2.17.1