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    Subject[PATCH 4.4 11/46] NET: mkiss: Fix panic
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    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;

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