* [PATCH] net/rose: fix NULL ax25_cb kernel panic
@ 2019-01-25 10:46 Dmitry Vyukov
2019-01-27 18:41 ` David Miller
0 siblings, 1 reply; 2+ messages in thread
From: Dmitry Vyukov @ 2019-01-25 10:46 UTC (permalink / raw)
To: f6bvp, davem, linux-hams, netdev
Cc: Dmitry Vyukov, syzbot+1a2c456a1ea08fa5b5f7, Ralf Baechle, linux-kernel
From: Bernard Pidoux <f6bvp@free.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@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
---
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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] net/rose: fix NULL ax25_cb kernel panic
2019-01-25 10:46 [PATCH] net/rose: fix NULL ax25_cb kernel panic Dmitry Vyukov
@ 2019-01-27 18:41 ` David Miller
0 siblings, 0 replies; 2+ messages in thread
From: David Miller @ 2019-01-27 18:41 UTC (permalink / raw)
To: dvyukov
Cc: f6bvp, linux-hams, netdev, dvyukov, syzbot+1a2c456a1ea08fa5b5f7,
ralf, linux-kernel
From: Dmitry Vyukov <dvyukov@gmail.com>
Date: Fri, 25 Jan 2019 11:46:40 +0100
> From: Bernard Pidoux <f6bvp@free.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@free.fr>
> Acked-by: Dmitry Vyukov <dvyukov@google.com>
> Reported-by: syzbot+1a2c456a1ea08fa5b5f7@syzkaller.appspotmail.com
Applied and queued up for -stable, thanks.
^ permalink raw reply [flat|nested] 2+ messages in thread
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