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: Shmulik 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: David S. Miller <davem@davemloft.net>
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@ -4528,13 +4528,18 @@ EXPORT_SYMBOL(skb_ensure_writable);
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int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci)
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{
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struct vlan_hdr *vhdr;
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unsigned int offset = skb->data - skb_mac_header(skb);
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int offset = skb->data - skb_mac_header(skb);
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int err;
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__skb_push(skb, offset);
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if (WARN_ONCE(offset,
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"__skb_vlan_pop got skb with skb->data not at mac header (offset %d)\n",
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offset)) {
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return -EINVAL;
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}
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err = skb_ensure_writable(skb, VLAN_ETH_HLEN);
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if (unlikely(err))
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goto pull;
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return err;
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skb_postpull_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
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@ -4551,13 +4556,14 @@ int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci)
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skb_set_network_header(skb, ETH_HLEN);
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skb_reset_mac_len(skb);
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pull:
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__skb_pull(skb, offset);
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return err;
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}
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EXPORT_SYMBOL(__skb_vlan_pop);
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/* Pop a vlan tag either from hwaccel or from payload.
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* Expects skb->data at mac header.
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*/
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int skb_vlan_pop(struct sk_buff *skb)
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{
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u16 vlan_tci;
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@ -4588,29 +4594,30 @@ int skb_vlan_pop(struct sk_buff *skb)
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}
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EXPORT_SYMBOL(skb_vlan_pop);
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/* Push a vlan tag either into hwaccel or into payload (if hwaccel tag present).
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* Expects skb->data at mac header.
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*/
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int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
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{
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if (skb_vlan_tag_present(skb)) {
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unsigned int offset = skb->data - skb_mac_header(skb);
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int offset = skb->data - skb_mac_header(skb);
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int err;
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/* __vlan_insert_tag expect skb->data pointing to mac header.
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* So change skb->data before calling it and change back to
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* original position later
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*/
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__skb_push(skb, offset);
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if (WARN_ONCE(offset,
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"skb_vlan_push got skb with skb->data not at mac header (offset %d)\n",
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offset)) {
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return -EINVAL;
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}
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err = __vlan_insert_tag(skb, skb->vlan_proto,
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skb_vlan_tag_get(skb));
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if (err) {
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__skb_pull(skb, offset);
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if (err)
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return err;
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}
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skb->protocol = skb->vlan_proto;
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skb->mac_len += VLAN_HLEN;
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skb_postpush_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
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__skb_pull(skb, offset);
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}
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__vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);
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return 0;
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