Re: [PATCH] ipv4: fib: avoid NULL dereference

[David Ahern]

On 7/6/18 8:28 AM, Mark Rutland wrote:
> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
> index 5bc0c89e81e4..8d98c8162554 100644
> --- a/net/ipv4/fib_trie.c
> +++ b/net/ipv4/fib_trie.c
> @@ -497,11 +497,11 @@ static void tnode_free(struct key_vector *tn)
>  	struct callback_head *head = &tn_info(tn)->rcu;
>  
>  	while (head) {
> +		tn = container_of(head, struct tnode, rcu)->kv;
> +
>  		head = head->next;
>  		tnode_free_size += TNODE_SIZE(1ul << tn->bits);
>  		node_free(tn);

you are changing tn before the above 2 calls are made on the tn passed in


> -
> -		tn = container_of(head, struct tnode, rcu)->kv;
>  	}
>  
>  	if (tnode_free_size >= PAGE_SIZE * sync_pages) {
>