3.18-stable review patch. If anyone has any objections, please let me know.
------------------ From: Bernard Pidoux <[email protected]> [ 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 <[email protected]> Acked-by: Dmitry Vyukov <[email protected]> Reported-by: [email protected] Cc: "David S. Miller" <[email protected]> Cc: Ralf Baechle <[email protected]> Cc: Bernard Pidoux <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- net/rose/rose_route.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/net/rose/rose_route.c +++ b/net/rose/rose_route.c @@ -849,6 +849,7 @@ 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) { @@ -866,6 +867,10 @@ 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 &&
