linux-kernel - [PATCH] dma-buf/udmabuf: Fix NULL pointer dereference in udmabuf

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Date:   Tue, 4 Sep 2018 14:07:49 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Gerd Hoffmann <kraxel@...hat.com>,
        Sumit Semwal <sumit.semwal@...aro.org>
Cc:     linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] dma-buf/udmabuf: Fix NULL pointer dereference in
 udmabuf_create

There is a potential execution path in which pointer memfd is NULL when
passed as argument to fput(), hence there is a NULL pointer dereference
in fput().

Fix this by null checking *memfd* before calling fput().

Addresses-Coverity-ID: 1473174 ("Explicit null dereferenced")
Fixes: fbb0de795078 ("Add udmabuf misc device")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/dma-buf/udmabuf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 8e24204..2e85022 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -194,7 +194,8 @@ static long udmabuf_create(struct udmabuf_create_list *head,
 	while (pgbuf > 0)
 		put_page(ubuf->pages[--pgbuf]);
 err_free_ubuf:
-	fput(memfd);
+	if (memfd)
+		fput(memfd);
 	kfree(ubuf->pages);
 	kfree(ubuf);
 	return ret;
-- 
2.7.4