Bluetooth: 6lowpan: Fix kernel NULL pointer dereferences

The fixes provided in this patch assigns a valid net_device structure to
skb before dispatching it for further processing.

Scenario #1:
============

Bluetooth 6lowpan receives an uncompressed IPv6 header, and dispatches it
to netif. The following error occurs:

Null pointer dereference error #1 crash log:

[  845.854013] BUG: unable to handle kernel NULL pointer dereference at
               0000000000000048
[  845.855785] IP: [<ffffffff816e3d36>] enqueue_to_backlog+0x56/0x240
...
[  845.909459] Call Trace:
[  845.911678]  [<ffffffff816e3f64>] netif_rx_internal+0x44/0xf0

The first modification fixes the NULL pointer dereference error by
assigning dev to the local_skb in order to set a valid net_device before
processing the skb by netif_rx_ni().

Scenario #2:
============

Bluetooth 6lowpan receives an UDP compressed message which needs further
decompression by nhc_udp. The following error occurs:

Null pointer dereference error #2 crash log:

[   63.295149] BUG: unable to handle kernel NULL pointer dereference at
               0000000000000840
[   63.295931] IP: [<ffffffffc0559540>] udp_uncompress+0x320/0x626
               [nhc_udp]

The second modification fixes the NULL pointer dereference error by
assigning dev to the local_skb in the case of a udp compressed packet.
The 6lowpan udp_uncompress function expects that the net_device is set in
the skb when checking lltype.

Signed-off-by: Glenn Ruben Bakke <glenn.ruben.bakke@nordicsemi.no>
Signed-off-by: Lukasz Duda <lukasz.duda@nordicsemi.no>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Cc: stable@vger.kernel.org # 4.4+

1 files changed, 3 insertions, 1 deletions

diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
index d040365ba98e..58e1b3c97ed7 100644
--- a/net/bluetooth/6lowpan.c
+++ b/net/bluetooth/6lowpan.c
@@ -317,6 +317,7 @@ static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
 
                 local_skb->protocol = htons(ETH_P_IPV6);
                 local_skb->pkt_type = PACKET_HOST;
+                local_skb->dev = dev;
 
                 skb_set_transport_header(local_skb, sizeof(struct ipv6hdr));
 
@@ -335,6 +336,8 @@ static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
                 if (!local_skb)
                         goto drop;
 
+                local_skb->dev = dev;
+
                 ret = iphc_decompress(local_skb, dev, chan);
                 if (ret < 0) {
                         kfree_skb(local_skb);
@@ -343,7 +346,6 @@ static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
 
                 local_skb->protocol = htons(ETH_P_IPV6);
                 local_skb->pkt_type = PACKET_HOST;
-                local_skb->dev = dev;
 
                 if (give_skb_to_upper(local_skb, dev)
                                 != NET_RX_SUCCESS) {