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Message-Id: <20190125104640.253862-1-dvyukov@gmail.com>
Date: Fri, 25 Jan 2019 11:46:40 +0100
From: Dmitry Vyukov <dvyukov@...il.com>
To: f6bvp@...e.fr, davem@...emloft.net, linux-hams@...r.kernel.org,
netdev@...r.kernel.org
Cc: Dmitry Vyukov <dvyukov@...gle.com>,
syzbot+1a2c456a1ea08fa5b5f7@...kaller.appspotmail.com,
Ralf Baechle <ralf@...ux-mips.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH] net/rose: fix NULL ax25_cb kernel panic
From: Bernard Pidoux <f6bvp@...e.fr>
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@...e.fr>
Acked-by: Dmitry Vyukov <dvyukov@...gle.com>
Reported-by: syzbot+1a2c456a1ea08fa5b5f7@...kaller.appspotmail.com
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: Bernard Pidoux <f6bvp@...e.fr>
Cc: linux-hams@...r.kernel.org
Cc: netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
net/rose/rose_route.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/net/rose/rose_route.c b/net/rose/rose_route.c
index 77e9f85a2c92..f2ff21d7df08 100644
--- a/net/rose/rose_route.c
+++ b/net/rose/rose_route.c
@@ -850,6 +850,7 @@ void rose_link_device_down(struct net_device *dev)
/*
* 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, ax25_cb *ax25)
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 &&
--
2.20.1.495.gaa96b0ce6b-goog
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