Re: [PATCH] kfree_skb() bug in 2.4.22

Tobias DiPasquale wrote:

Hi all,

I was debugging one of my iptables/netfilter modules yesterday and I
came across this bug in kfree_skb(). One of my functions returns a
struct skbuff * on success and NULL on failure. When it failed, the code
calling said function attempted to free the struct skbuff *, which at
that point was NULL. This produced a kernel panic. I investigated the
problem and found that, not only should I be checking for a NULL pointer
when freeing the struct skbuff *, but the actual cause of the panic was
because kfree_skb() and kfree_skb_fast() do not check for skb==NULL,
either. They immediately attempt to dereference the users field of the
struct skbuff * in order to decrement that reference counter. 

I would prefer that you fix your code instead, to not pass NULL to 
kfree_skb()...