[PATCH 4.14 10/21] net: qualcomm: rmnet: Fix incorrect assignment of real_dev

Greg Kroah-Hartman
2018-11-21T19:08:56Z

From: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>

[ Upstream commit d02854dc1999ed3e7fd79ec700c64ac23ac0c458 ]

A null dereference was observed when a sysctl was being set
from userspace and rmnet was stuck trying to complete some actions
in the NETDEV_REGISTER callback. This is because the real_dev is set
only after the device registration handler completes.

sysctl call stack -

<6> Unable to handle kernel NULL pointer dereference at
virtual address 00000108
<2> pc : rmnet_vnd_get_iflink+0x1c/0x28
<2> lr : dev_get_iflink+0x2c/0x40
<2> rmnet_vnd_get_iflink+0x1c/0x28
<2> inet6_fill_ifinfo+0x15c/0x234
<2> inet6_ifinfo_notify+0x68/0xd4
<2> ndisc_ifinfo_sysctl_change+0x1b8/0x234
<2> proc_sys_call_handler+0xac/0x100
<2> proc_sys_write+0x3c/0x4c
<2> __vfs_write+0x54/0x14c
<2> vfs_write+0xcc/0x188
<2> SyS_write+0x60/0xc0
<2> el0_svc_naked+0x34/0x38

device register call stack -

<2> notifier_call_chain+0x84/0xbc
<2> raw_notifier_call_chain+0x38/0x48
<2> call_netdevice_notifiers_info+0x40/0x70
<2> call_netdevice_notifiers+0x38/0x60
<2> register_netdevice+0x29c/0x3d8
<2> rmnet_vnd_newlink+0x68/0xe8
<2> rmnet_newlink+0xa0/0x160
<2> rtnl_newlink+0x57c/0x6c8
<2> rtnetlink_rcv_msg+0x1dc/0x328
<2> netlink_rcv_skb+0xac/0x118
<2> rtnetlink_rcv+0x24/0x30
<2> netlink_unicast+0x158/0x1f0
<2> netlink_sendmsg+0x32c/0x338
<2> sock_sendmsg+0x44/0x60
<2> SyS_sendto+0x150/0x1ac
<2> el0_svc_naked+0x34/0x38

Fixes: b752eff5be24 ("net: qualcomm: rmnet: Implement ndo_get_iflink")
Signed-off-by: Sean Tranchetti <stranche@codeaurora.org>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c
@@ -102,12 +102,14 @@ int rmnet_vnd_newlink(u8 id, struct net_
struct rmnet_port *port,
struct net_device *real_dev)
{
- struct rmnet_priv *priv;
+ struct rmnet_priv *priv = netdev_priv(rmnet_dev);
int rc;

if (port->rmnet_devices[id])
return -EINVAL;

+ priv->real_dev = real_dev;
+
rc = register_netdevice(rmnet_dev);
if (!rc) {
port->rmnet_devices[id] = rmnet_dev;
@@ -115,9 +117,7 @@ int rmnet_vnd_newlink(u8 id, struct net_

rmnet_dev->rtnl_link_ops = &rmnet_link_ops;

- priv = netdev_priv(rmnet_dev);
priv->mux_id = id;
- priv->real_dev = real_dev;

netdev_dbg(rmnet_dev, "rmnet dev created\n");
}