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Commit b6a79208 authored by Shmulik Ladkani's avatar Shmulik Ladkani Committed by David S. Miller
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net: skbuff: Limit skb_vlan_pop/push() to expect skb->data at mac header 



skb_vlan_pop/push were too generic, trying to support the cases where
skb->data is at mac header, and cases where skb->data is arbitrarily
elsewhere.

Supporting an arbitrary skb->data was complex and bogus:
 - It failed to unwind skb->data to its original location post actual
   pop/push.
   (Also, semantic is not well defined for unwinding: If data was into
    the eth header, need to use same offset from start; But if data was
    at network header or beyond, need to adjust the original offset
    according to the push/pull)
 - It mangled the rcsum post actual push/pop, without taking into account
   that the eth bytes might already have been pulled out of the csum.

Most callers (ovs, bpf) already had their skb->data at mac_header upon
invoking skb_vlan_pop/push.
Last caller that failed to do so (act_vlan) has been recently fixed.

Therefore, to simplify things, no longer support arbitrary skb->data
inputs for skb_vlan_pop/push().

skb->data is expected to be exactly at mac_header; WARN otherwise.

Signed-off-by: default avatarShmulik Ladkani <shmulik.ladkani@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Pravin Shelar <pshelar@ovn.org>
Cc: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f39acc84

net/core/skbuff.c

+22 −15
Original line number Diff line number Diff line
@@ -4528,13 +4528,18 @@ EXPORT_SYMBOL(skb_ensure_writable); 
int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci)

{

	struct vlan_hdr *vhdr;

	unsigned int offset = skb->data - skb_mac_header(skb);

	int offset = skb->data - skb_mac_header(skb);

	int err;



	__skb_push(skb, offset);

	if (WARN_ONCE(offset,

		      "__skb_vlan_pop got skb with skb->data not at mac header (offset %d)\n",

		      offset)) {

		return -EINVAL;

	}



	err = skb_ensure_writable(skb, VLAN_ETH_HLEN);

	if (unlikely(err))

		goto pull;

		return err;



	skb_postpull_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
@@ -4551,13 +4556,14 @@ int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci) 
		skb_set_network_header(skb, ETH_HLEN);



	skb_reset_mac_len(skb);

pull:

	__skb_pull(skb, offset);



	return err;

}

EXPORT_SYMBOL(__skb_vlan_pop);



/* Pop a vlan tag either from hwaccel or from payload.

 * Expects skb->data at mac header.

 */

int skb_vlan_pop(struct sk_buff *skb)

{

	u16 vlan_tci;
@@ -4588,29 +4594,30 @@ int skb_vlan_pop(struct sk_buff *skb) 
}

EXPORT_SYMBOL(skb_vlan_pop);



/* Push a vlan tag either into hwaccel or into payload (if hwaccel tag present).

 * Expects skb->data at mac header.

 */

int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)

{

	if (skb_vlan_tag_present(skb)) {

		unsigned int offset = skb->data - skb_mac_header(skb);

		int offset = skb->data - skb_mac_header(skb);

		int err;



		/* __vlan_insert_tag expect skb->data pointing to mac header.

		 * So change skb->data before calling it and change back to

		 * original position later

		 */

		__skb_push(skb, offset);

		if (WARN_ONCE(offset,

			      "skb_vlan_push got skb with skb->data not at mac header (offset %d)\n",

			      offset)) {

			return -EINVAL;

		}



		err = __vlan_insert_tag(skb, skb->vlan_proto,

					skb_vlan_tag_get(skb));

		if (err) {

			__skb_pull(skb, offset);

		if (err)

			return err;

		}



		skb->protocol = skb->vlan_proto;

		skb->mac_len += VLAN_HLEN;



		skb_postpush_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);

		__skb_pull(skb, offset);

	}

	__vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);

	return 0;