Patch "NET: mkiss: Fix panic" 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

NET: mkiss: Fix panic

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:
net-mkiss-fix-panic.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: Ralf Baechle <[email protected]>
Date: Tue, 23 May 2017 21:53:40 -0400
Subject: NET: mkiss: Fix panic

From: Ralf Baechle <[email protected]>

[ Upstream commit 7ba1b689038726d34e3244c1ac9e2e18c2ea4787 ]

If a USB-to-serial adapter is unplugged, the driver re-initializes, with dev->hard_header_len and dev->addr_len set to zero, instead of the correct values. If then a packet is sent through the half-dead interface, the kernel will panic due to running out of headroom in the skb when pushing for the AX.25 headers resulting in this panic:

[<c0595468>] (skb_panic) from [<c0401f70>] (skb_push+0x4c/0x50) [<c0401f70>] (skb_push) from [<bf0bdad4>] (ax25_hard_header+0x34/0xf4 [ax25]) [<bf0bdad4>] (ax25_hard_header [ax25]) from [<bf0d05d4>] (ax_header+0x38/0x40 [mkiss]) [<bf0d05d4>] (ax_header [mkiss]) from [<c041b584>] (neigh_compat_output+0x8c/0xd8) [<c041b584>] (neigh_compat_output) from [<c043e7a8>] (ip_finish_output+0x2a0/0x914) [<c043e7a8>] (ip_finish_output) from [<c043f948>] (ip_output+0xd8/0xf0) [<c043f948>] (ip_output) from [<c043f04c>] (ip_local_out_sk+0x44/0x48)

This patch makes mkiss behave like the 6pack driver. 6pack does not panic. In 6pack.c sp_setup() (same function name here) the values for dev->hard_header_len and dev->addr_len are set to the same values as in my mkiss patch.

[[email protected]: Massages original submission to conform to the usual standards for patch submissions.]

---
 drivers/net/hamradio/mkiss.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -648,8 +648,8 @@ static void ax_setup(struct net_device *
 {
 	/* Finish setting up the DEVICE info. */
 	dev->mtu             = AX_MTU;
-	dev->hard_header_len = 0;
-	dev->addr_len        = 0;
+	dev->hard_header_len = AX25_MAX_HEADER_LEN;
+	dev->addr_len        = AX25_ADDR_LEN;
 	dev->type            = ARPHRD_AX25;
 	dev->tx_queue_len    = 10;
 	dev->header_ops      = &ax25_header_ops;

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

queue-4.4/net-fix-proc-net-arp-for-ax.25.patch
queue-4.4/net-mkiss-fix-panic.patch