[B.A.T.M.A.N.] [PATCH 10/10] batman-adv: fix potential kernel paging error for unicast transmissions

Antonio Quartulli
2014-02-17T20:48:49Z

batadv_send_skb_prepare_unicast(_4addr) might reallocate the
skb's data. If it does then our ethhdr pointer is not valid
anymore in batadv_send_skb_unicast(), resulting in a kernel
paging error.

Fixing this by refetching the ethhdr pointer after the
potential reallocation.

Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>
---
net/batman-adv/send.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/net/batman-adv/send.c b/net/batman-adv/send.c
index 579f5f0..843febd 100644
--- a/net/batman-adv/send.c
+++ b/net/batman-adv/send.c
@@ -254,9 +254,9 @@ static int batadv_send_skb_unicast(struct batadv_priv *bat_priv,
struct batadv_orig_node *orig_node,
unsigned short vid)
{
- struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
+ struct ethhdr *ethhdr;
struct batadv_unicast_packet *unicast_packet;
- int ret = NET_XMIT_DROP;
+ int ret = NET_XMIT_DROP, hdr_size;

if (!orig_node)
goto out;
@@ -265,12 +265,16 @@ static int batadv_send_skb_unicast(struct batadv_priv *bat_priv,
case BATADV_UNICAST:
if (!batadv_send_skb_prepare_unicast(skb, orig_node))
goto out;
+
+ hdr_size = sizeof(*unicast_packet);
break;
case BATADV_UNICAST_4ADDR:
if (!batadv_send_skb_prepare_unicast_4addr(bat_priv, skb,
orig_node,
packet_subtype))
goto out;
+
+ hdr_size = sizeof(struct batadv_unicast_4addr_packet);
break;
default:
/* this function supports UNICAST and UNICAST_4ADDR only. It
@@ -279,6 +283,7 @@ static int batadv_send_skb_unicast(struct batadv_priv *bat_priv,
goto out;
}

+ ethhdr = (struct ethhdr *)(skb->data + hdr_size);
unicast_packet = (struct batadv_unicast_packet *)skb->data;

/* inform the destination node that we are still missing a correct route
--
1.8.5.3