Patch "Bluetooth: 6lowpan: Fix kernel NULL pointer dereferences" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

Bluetooth: 6lowpan: Fix kernel NULL pointer dereferences

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
bluetooth-6lowpan-fix-kernel-null-pointer-dereferences.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Glenn Ruben Bakke <[email protected]>
Date: Wed, 13 Jan 2016 16:41:42 +0100
Subject: Bluetooth: 6lowpan: Fix kernel NULL pointer dereferences

From: Glenn Ruben Bakke <[email protected]>

commit 4c58f3282e3de43d34f8955f8eca676294380bf9 upstream.

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.

---
 net/bluetooth/6lowpan.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

@@ -317,6 +317,7 @@ static int recv_pkt(struct sk_buff *skb,
 
 		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,
 		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,
 
 		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) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/bluetooth-6lowpan-fix-kernel-null-pointer-dereferences.patch queue-4.4/bluetooth-6lowpan-fix-handling-of-uncompressed-ipv6-packets.patch