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Commit 8c057efa authored by Edward Cree's avatar Edward Cree Committed by David S. Miller
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net: core: fix uses-after-free in list processing 



In netif_receive_skb_list_internal(), all of skb_defer_rx_timestamp(),
 do_xdp_generic() and enqueue_to_backlog() can lead to kfree(skb).  Thus,
 we cannot wait until after they return to remove the skb from the list;
 instead, we remove it first and, in the pass case, add it to a sublist
 afterwards.
In the case of enqueue_to_backlog() we have already decided not to pass
 when we call the function, so we do not need a sublist.

Fixes: 7da517a3 ("net: core: Another step of skb receive list processing")
Reported-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: default avatarEdward Cree <ecree@solarflare.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c47078d6

net/core/dev.c

+13 −8
Original line number Diff line number Diff line
@@ -4982,25 +4982,30 @@ static void netif_receive_skb_list_internal(struct list_head *head) 
{

	struct bpf_prog *xdp_prog = NULL;

	struct sk_buff *skb, *next;

	struct list_head sublist;



	INIT_LIST_HEAD(&sublist);

	list_for_each_entry_safe(skb, next, head, list) {

		net_timestamp_check(netdev_tstamp_prequeue, skb);

		if (skb_defer_rx_timestamp(skb))

			/* Handled, remove from list */

		list_del(&skb->list);

		if (!skb_defer_rx_timestamp(skb))

			list_add_tail(&skb->list, &sublist);

	}

	list_splice_init(&sublist, head);



	if (static_branch_unlikely(&generic_xdp_needed_key)) {

		preempt_disable();

		rcu_read_lock();

		list_for_each_entry_safe(skb, next, head, list) {

			xdp_prog = rcu_dereference(skb->dev->xdp_prog);

			if (do_xdp_generic(xdp_prog, skb) != XDP_PASS)

				/* Dropped, remove from list */

			list_del(&skb->list);

			if (do_xdp_generic(xdp_prog, skb) == XDP_PASS)

				list_add_tail(&skb->list, &sublist);

		}

		rcu_read_unlock();

		preempt_enable();

		/* Put passed packets back on main list */

		list_splice_init(&sublist, head);

	}



	rcu_read_lock();
@@ -5011,9 +5016,9 @@ static void netif_receive_skb_list_internal(struct list_head *head) 
			int cpu = get_rps_cpu(skb->dev, skb, &rflow);



			if (cpu >= 0) {

				enqueue_to_backlog(skb, cpu, &rflow->last_qtail);

				/* Handled, remove from list */

				/* Will be handled, remove from list */

				list_del(&skb->list);

				enqueue_to_backlog(skb, cpu, &rflow->last_qtail);

			}

		}

	}