4.20-stable review patch. If anyone has any objections, please let me know.
------------------
From: Bernard Pidoux <f6...@free.fr>
[ Upstream commit b0cf029234f9b18e10703ba5147f0389c382bccc ]
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 <f6...@free.fr>
Acked-by: Dmitry Vyukov <dvyu...@google.com>
Reported-by: syzbot+1a2c456a1ea08fa5b...@syzkaller.appspotmail.com
Cc: "David S. Miller" <da...@davemloft.net>
Cc: Ralf Baechle <r...@linux-mips.org>
Cc: Bernard Pidoux <f6...@free.fr>
Cc: linux-hams@vger.kernel.org
Cc: net...@vger.kernel.org
Cc: linux-ker...@vger.kernel.org
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
net/rose/rose_route.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/net/rose/rose_route.c
+++ b/net/rose/rose_route.c
@@ -850,6 +850,7 @@ 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)
{
@@ -867,6 +868,10 @@ 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 &&
