Even Batman should not dereference NULL pointers
Commit Message
There's a problem in net/batman-adv/unicast.c::frag_send_skb().
dev_alloc_skb() allocates memory and may fail, thus returning NULL. If
this happens we'll pass a NULL pointer on to skb_split() which in turn
hands it to skb_split_inside_header() from where it gets passed to
skb_put() that lets skb_tail_pointer() play with it and that function
dereferences it. And thus the bat dies.
While I was at it I also moved the call to dev_alloc_skb() above the
assignment to 'unicast_packet' since there's no reason to do that
assignment if the memory allocation fails.
Signed-off-by: Jesper Juhl <jj@chaosbits.net>
---
unicast.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
Comments
On Thursday 13 January 2011 21:53:38 Jesper Juhl wrote:
> There's a problem in net/batman-adv/unicast.c::frag_send_skb().
> dev_alloc_skb() allocates memory and may fail, thus returning NULL. If
> this happens we'll pass a NULL pointer on to skb_split() which in turn
> hands it to skb_split_inside_header() from where it gets passed to
> skb_put() that lets skb_tail_pointer() play with it and that function
> dereferences it. And thus the bat dies.
>
> While I was at it I also moved the call to dev_alloc_skb() above the
> assignment to 'unicast_packet' since there's no reason to do that
> assignment if the memory allocation fails.
Applied
Thanks,
Sven
@@ -229,10 +229,12 @@ int frag_send_skb(struct sk_buff *skb, struct bat_priv *bat_priv,
if (!bat_priv->primary_if)
goto dropped;
- unicast_packet = (struct unicast_packet *) skb->data;
+ frag_skb = dev_alloc_skb(data_len - (data_len / 2) + ucf_hdr_len);
+ if (!frag_skb)
+ goto dropped;
+ unicast_packet = (struct unicast_packet *) skb->data;
memcpy(&tmp_uc, unicast_packet, uc_hdr_len);
- frag_skb = dev_alloc_skb(data_len - (data_len / 2) + ucf_hdr_len);
skb_split(skb, frag_skb, data_len / 2);
if (my_skb_head_push(skb, ucf_hdr_len - uc_hdr_len) < 0 ||