Patch "NET: mkiss: Fix panic" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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 <stable@vger.kernel.org> know about it.


>From foo@baz Thu Jun 15 11:13:01 CEST 2017
From: Ralf Baechle <ralf@linux-mips.org>
Date: Tue, 23 May 2017 21:53:40 -0400
Subject: NET: mkiss: Fix panic

From: Ralf Baechle <ralf@linux-mips.org>


[ 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.

[ralf@linux-mips.org: Massages original submission to conform to the usual
standards for patch submissions.]

Signed-off-by: Thomas Osterried <thomas@osterried.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/hamradio/mkiss.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/hamradio/mkiss.c
+++ b/drivers/net/hamradio/mkiss.c
@@ -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 ralf@linux-mips.org are

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