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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Colin Ian King <colin.king@canonical.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 096/243] net: qualcomm: rmnet: move null check on dev before dereferecing it
Date:   Wed, 11 Dec 2019 16:04:18 +0100
Message-Id: <20191211150345.597562936@linuxfoundation.org>
In-Reply-To: <20191211150339.185439726@linuxfoundation.org>
References: <20191211150339.185439726@linuxfoundation.org>
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From: Colin Ian King <colin.king@canonical.com>

[ Upstream commit 3c18aa1464f9232d6abac8d7b4540f61b0658d62 ]

Currently dev is dereferenced by the call dev_net(dev) before dev is null
checked.  Fix this by null checking dev before the potential null
pointer dereference.

Detected by CoverityScan, CID#1462955 ("Dereference before null check")

Fixes: 23790ef12082 ("net: qualcomm: rmnet: Allow to configure flags for existing devices")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
index f66d1255e36a2..4c476fac78358 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
@@ -301,10 +301,13 @@ static int rmnet_changelink(struct net_device *dev, struct nlattr *tb[],
 	struct rmnet_port *port;
 	u16 mux_id;
 
+	if (!dev)
+		return -ENODEV;
+
 	real_dev = __dev_get_by_index(dev_net(dev),
 				      nla_get_u32(tb[IFLA_LINK]));
 
-	if (!real_dev || !dev || !rmnet_is_real_dev_registered(real_dev))
+	if (!real_dev || !rmnet_is_real_dev_registered(real_dev))
 		return -ENODEV;
 
 	port = rmnet_get_port_rtnl(real_dev);
-- 
2.20.1