4.20-stable review patch. If anyone has any objections, please let me know.
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From: Bernard Pidoux f6bvp@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 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 --- 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 &&