Commit c0bbbdc3 authored by Boris Sukholitko's avatar Boris Sukholitko Committed by David S. Miller
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__netif_receive_skb_core: pass skb by reference 



__netif_receive_skb_core may change the skb pointer passed into it (e.g.
in rx_handler). The original skb may be freed as a result of this
operation.

The callers of __netif_receive_skb_core may further process original skb
by using pt_prev pointer returned by __netif_receive_skb_core thus
leading to unpleasant effects.

The solution is to pass skb by reference into __netif_receive_skb_core.

v2: Added Fixes tag and comment regarding ppt_prev and skb invariant.

Fixes: 88eb1944 ("net: core: propagate SKB lists through packet_type lookup")
Signed-off-by: default avatarBoris Sukholitko <boris.sukholitko@broadcom.com>
Acked-by: default avatarEdward Cree <ecree@solarflare.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 88d7fcfa

net/core/dev.c

+15 −5
Original line number Diff line number Diff line
@@ -4988,11 +4988,12 @@ static inline int nf_ingress(struct sk_buff *skb, struct packet_type **pt_prev, 
	return 0;

}



static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc,

static int __netif_receive_skb_core(struct sk_buff **pskb, bool pfmemalloc,

				    struct packet_type **ppt_prev)

{

	struct packet_type *ptype, *pt_prev;

	rx_handler_func_t *rx_handler;

	struct sk_buff *skb = *pskb;

	struct net_device *orig_dev;

	bool deliver_exact = false;

	int ret = NET_RX_DROP;
@@ -5023,8 +5024,10 @@ another_round: 
		ret2 = do_xdp_generic(rcu_dereference(skb->dev->xdp_prog), skb);

		preempt_enable();



		if (ret2 != XDP_PASS)

			return NET_RX_DROP;

		if (ret2 != XDP_PASS) {

			ret = NET_RX_DROP;

			goto out;

		}

		skb_reset_mac_len(skb);

	}
@@ -5174,6 +5177,13 @@ drop: 
	}



out:

	/* The invariant here is that if *ppt_prev is not NULL

	 * then skb should also be non-NULL.

	 *

	 * Apparently *ppt_prev assignment above holds this invariant due to

	 * skb dereferencing near it.

	 */

	*pskb = skb;

	return ret;

}
@@ -5183,7 +5193,7 @@ static int __netif_receive_skb_one_core(struct sk_buff *skb, bool pfmemalloc) 
	struct packet_type *pt_prev = NULL;

	int ret;



	ret = __netif_receive_skb_core(skb, pfmemalloc, &pt_prev);

	ret = __netif_receive_skb_core(&skb, pfmemalloc, &pt_prev);

	if (pt_prev)

		ret = INDIRECT_CALL_INET(pt_prev->func, ipv6_rcv, ip_rcv, skb,

					 skb->dev, pt_prev, orig_dev);
@@ -5261,7 +5271,7 @@ static void __netif_receive_skb_list_core(struct list_head *head, bool pfmemallo 
		struct packet_type *pt_prev = NULL;



		skb_list_del_init(skb);

		__netif_receive_skb_core(skb, pfmemalloc, &pt_prev);

		__netif_receive_skb_core(&skb, pfmemalloc, &pt_prev);

		if (!pt_prev)

			continue;

		if (pt_curr != pt_prev || od_curr != orig_dev) {

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