On Sun, 2016-12-18 at 11:00 -0800, Mahesh Bandewar wrote:
> From: Mahesh Bandewar <mahe...@google.com>
>
> In an IPvlan setup when master is set in loopback mode e.g.
>
> ethtool -K eth0 set loopback on
>
> where eth0 is master device for IPvlan setup.
>
> The failure actually happens while processing mulitcast packets
> but that's a result of unconditionally queueing packets without
> ensuring ether-header is part of the linear part of skb.
>
> This patch forces this check at the reception and drops packets
> which fail this check before queuing them.
>
> ------------[ cut here ]------------
> kernel BUG at include/linux/skbuff.h:1737!
> Call Trace:
> [<ffffffff921fbbc2>] dev_forward_skb+0x92/0xd0
> [<ffffffffc031ac65>] ipvlan_process_multicast+0x395/0x4c0 [ipvlan]
> [<ffffffffc031a9a7>] ? ipvlan_process_multicast+0xd7/0x4c0 [ipvlan]
> [<ffffffff91cdfea7>] ? process_one_work+0x147/0x660
> [<ffffffff91cdff09>] process_one_work+0x1a9/0x660
> [<ffffffff91cdfea7>] ? process_one_work+0x147/0x660
> [<ffffffff91ce086d>] worker_thread+0x11d/0x360
> [<ffffffff91ce0750>] ? rescuer_thread+0x350/0x350
> [<ffffffff91ce960b>] kthread+0xdb/0xe0
> [<ffffffff91c05c70>] ? _raw_spin_unlock_irq+0x30/0x50
> [<ffffffff91ce9530>] ? flush_kthread_worker+0xc0/0xc0
> [<ffffffff92348b7a>] ret_from_fork+0x9a/0xd0
> [<ffffffff91ce9530>] ? flush_kthread_worker+0xc0/0xc0
>
> Signed-off-by: Mahesh Bandewar <mahe...@google.com>
> ---
> v1->v2: commit log update
>
> drivers/net/ipvlan/ipvlan_core.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/net/ipvlan/ipvlan_core.c
> b/drivers/net/ipvlan/ipvlan_core.c
> index b4e990743e1d..4294fc1f5564 100644
> --- a/drivers/net/ipvlan/ipvlan_core.c
> +++ b/drivers/net/ipvlan/ipvlan_core.c
> @@ -660,6 +660,9 @@ rx_handler_result_t ipvlan_handle_frame(struct sk_buff
> **pskb)
> if (!port)
> return RX_HANDLER_PASS;
>
> + if (unlikely(!pskb_may_pull(skb, sizeof(struct ethhdr))))
> + goto out;
> +
> switch (port->mode) {
> case IPVLAN_MODE_L2:
> return ipvlan_handle_mode_l2(pskb, port);
> @@ -672,6 +675,8 @@ rx_handler_result_t ipvlan_handle_frame(struct sk_buff
> **pskb)
> /* Should not reach here */
> WARN_ONCE(true, "ipvlan_handle_frame() called for mode = [%hx]\n",
> port->mode);
> +
> +out:
> kfree_skb(skb);
> return RX_HANDLER_CONSUMED;
> }
There is something funky here.
When rx_handler() is called, we must have pulled Ethernet header
already.
Is this because RX_HANDLER_ANOTHER is returned in some cases, while it
should not ?
It looks like you added a pskb_may_pull() at a wrong place. Sure it
might fix the crash, but it looks weird here.
