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Merge branch 'vlan-fix'

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Toshiaki Makita says:

====================
Fix vlan tag handling for vlan packets without ethernet headers

Eric Dumazet reported syzbot found a new bug which leads to underflow of
size argument of memmove(), causing crash[1]. This can be triggered by tun
devices.

The underflow happened because skb_vlan_untag() did not expect vlan packets
without ethernet headers, and tun can produce such packets.
I also checked vlan_insert_inner_tag() and found a similar bug.

This series fixes these problems.

[1] https://marc.info/?l=linux-netdev&m=152221753920510&w=2
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2018-03-30 12:36:28 -04:00
commit 52a9692a43
2 changed files with 17 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
include/linux/if_vlan.h
View File

@ -323,13 +323,24 @@ static inline int __vlan_insert_inner_tag(struct sk_buff *skb,
skb_push(skb, VLAN_HLEN);
/* Move the mac header sans proto to the beginning of the new header. */
memmove(skb->data, skb->data + VLAN_HLEN, mac_len - ETH_TLEN);
if (likely(mac_len > ETH_TLEN))
memmove(skb->data, skb->data + VLAN_HLEN, mac_len - ETH_TLEN);
skb->mac_header -= VLAN_HLEN;
veth = (struct vlan_ethhdr *)(skb->data + mac_len - ETH_HLEN);
/* first, the ethernet type */
veth->h_vlan_proto = vlan_proto;
if (likely(mac_len >= ETH_TLEN)) {
/* h_vlan_encapsulated_proto should already be populated, and
* skb->data has space for h_vlan_proto
*/
veth->h_vlan_proto = vlan_proto;
} else {
/* h_vlan_encapsulated_proto should not be populated, and
* skb->data has no space for h_vlan_proto
*/
veth->h_vlan_encapsulated_proto = skb->protocol;
}
/* now, the TCI */
veth->h_vlan_TCI = htons(vlan_tci);

6
net/core/skbuff.c
View File

@ -5028,8 +5028,10 @@ static struct sk_buff *skb_reorder_vlan_header(struct sk_buff *skb)
}
mac_len = skb->data - skb_mac_header(skb);
memmove(skb_mac_header(skb) + VLAN_HLEN, skb_mac_header(skb),
mac_len - VLAN_HLEN - ETH_TLEN);
if (likely(mac_len > VLAN_HLEN + ETH_TLEN)) {
memmove(skb_mac_header(skb) + VLAN_HLEN, skb_mac_header(skb),
mac_len - VLAN_HLEN - ETH_TLEN);
}
skb->mac_header += VLAN_HLEN;
return skb;
}