linux-kernel - [PATCH v1] can: c_can: fix null-ptr-deref on ioctl()

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Date:   Mon,  6 Sep 2021 16:37:02 -0700
From:   Tong Zhang <ztong0001@...il.com>
To:     Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Tong Zhang <ztong0001@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Dario Binacchi <dariobin@...ero.it>, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] can: c_can: fix null-ptr-deref on ioctl()

the pdev maybe not a platform device, e.g. c_can_pci device,
in this case, calling to_platform_device() would not make sense.
Also, per the comment in drivers/net/can/c_can/c_can_ethtool.c, @bus_info
sould match dev_name() string, so I am replacing this with dev_name() to
fix this issue.

[    1.458583] BUG: unable to handle page fault for address: 0000000100000000
[    1.460921] RIP: 0010:strnlen+0x1a/0x30
[    1.466336]  ? c_can_get_drvinfo+0x65/0xb0 [c_can]
[    1.466597]  ethtool_get_drvinfo+0xae/0x360
[    1.466826]  dev_ethtool+0x10f8/0x2970
[    1.467880]  sock_ioctl+0xef/0x300

Fixes: 2722ac986e93 ("can: c_can: add ethtool support")
Signed-off-by: Tong Zhang <ztong0001@...il.com>
---
 drivers/net/can/c_can/c_can_ethtool.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/can/c_can/c_can_ethtool.c b/drivers/net/can/c_can/c_can_ethtool.c
index cd5f07fca2a5..377c7d2e7612 100644
--- a/drivers/net/can/c_can/c_can_ethtool.c
+++ b/drivers/net/can/c_can/c_can_ethtool.c
@@ -15,10 +15,8 @@ static void c_can_get_drvinfo(struct net_device *netdev,
 			      struct ethtool_drvinfo *info)
 {
 	struct c_can_priv *priv = netdev_priv(netdev);
-	struct platform_device *pdev = to_platform_device(priv->device);
-
 	strscpy(info->driver, "c_can", sizeof(info->driver));
-	strscpy(info->bus_info, pdev->name, sizeof(info->bus_info));
+	strscpy(info->bus_info, dev_name(priv->device), sizeof(info->bus_info));
 }
 
 static void c_can_get_ringparam(struct net_device *netdev,
-- 
2.25.1