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.
Introduced by 3275e7cc84fb0574e9662e8e74c3b1dab38f7143
("batman-adv: improve unicast packet (re)routing")
Reported-by: Linus Lüssing <[email protected]>
Signed-off-by: Antonio Quartulli <[email protected]>
---
***This patch is not supposed to be merged in the batman-adv
repository***
This is a substitutive patch that I am going to send to net
instead of the one that we have in maint (same subject).
I am doing this because the original patch together with all
the bugfixes that followed it cannot be considered a "simple
bugfix" anymore and I'd rather prefer to send it to net-next
with a later pull request.
This patch instead fixes the same problem but in a much
simpler way (does not use of eth_hdr()).
I sent it over the ml for peer review. If nobody has any
objection I will send it to net.
@Linus: I'd like to add your signed-off to this patch
because it is essentially your patch but just reworked a
bit. Please let me know what you think.
Cheers,
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..2f378a1 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_packet_4addr);
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;
}
+ eth_hdr = (struct eth_hdr *)(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
