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Date:   Mon,  4 Feb 2019 11:36:31 +0100
From:   Greg Kroah-Hartman <>
Cc:     Greg Kroah-Hartman <>,, Bernard Pidoux <>,
        Dmitry Vyukov <>,,
        "David S. Miller" <>,
        Ralf Baechle <>,,
Subject: [PATCH 4.4 38/65] net/rose: fix NULL ax25_cb kernel panic

4.4-stable review patch.  If anyone has any objections, please let me know.


From: Bernard Pidoux <>

[ Upstream commit b0cf029234f9b18e10703ba5147f0389c382bccc ]

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

        if (!rose_route_frame(skb, NULL)) {
                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
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.

Built kernel with CONFIG_ROSE=y.

Signed-off-by: Bernard Pidoux <>
Acked-by: Dmitry Vyukov <>
Cc: "David S. Miller" <>
Cc: Ralf Baechle <>
Cc: Bernard Pidoux <>
Signed-off-by: David S. Miller <>
Signed-off-by: Greg Kroah-Hartman <>
 net/rose/rose_route.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/net/rose/rose_route.c
+++ b/net/rose/rose_route.c
@@ -848,6 +848,7 @@ void rose_link_device_down(struct net_de
  *	Route a frame to an appropriate AX.25 connection.
+ *	A NULL ax25_cb indicates an internally generated frame.
 int rose_route_frame(struct sk_buff *skb, ax25_cb *ax25)
@@ -865,6 +866,10 @@ int rose_route_frame(struct sk_buff *skb
 	if (skb->len < ROSE_MIN_LEN)
 		return res;
+	if (!ax25)
+		return rose_loopback_queue(skb, NULL);
 	frametype = skb->data[2];
 	lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF);
 	if (frametype == ROSE_CALL_REQUEST &&

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