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net/rose: fix NULL ax25_cb kernel panic

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[ Upstream commit b0cf029234 ]

When an internally generated frame is handled by rose_xmit(),
rose_route_frame() is called:

        if (!rose_route_frame(skb, NULL)) {
                dev_kfree_skb(skb);
                stats->tx_errors++;
                return NETDEV_TX_OK;
        }

We have the same code sequence in Net/Rom where an internally generated
frame is handled by nr_xmit() calling nr_route_frame(skb, NULL).
However, in this function NULL argument is tested while it is not in
rose_route_frame().
Then kernel panic occurs later on when calling ax25cmp() with a NULL
ax25_cb argument as reported many times and recently with syzbot.

We need to test if ax25 is NULL before using it.

Testing:
Built kernel with CONFIG_ROSE=y.

Signed-off-by: Bernard Pidoux <f6bvp@free.fr>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Reported-by: syzbot+1a2c456a1ea08fa5b5f7@syzkaller.appspotmail.com
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Bernard Pidoux <f6bvp@free.fr>
Cc: linux-hams@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Bernard Pidoux 2019-01-25 11:46:40 +01:00 • committed by Greg Kroah-Hartman
commit 32d9062a88
1 changed files with 5 additions and 0 deletions
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