• Shmulik Ladkani's avatar
    net: skbuff: Remove errornous length validation in skb_vlan_pop() · 636c2628
    Shmulik Ladkani authored
    In 93515d53
      "net: move vlan pop/push functions into common code"
    skb_vlan_pop was moved from its private location in openvswitch to
    skbuff common code.
    
    In case skb has non hw-accel vlan tag, the original 'pop_vlan()' assured
    that skb->len is sufficient (if skb->len < VLAN_ETH_HLEN then pop was
    considered a no-op).
    
    This validation was moved as is into the new common 'skb_vlan_pop'.
    
    Alas, in its original location (openvswitch), there was a guarantee that
    'data' points to the mac_header, therefore the 'skb->len < VLAN_ETH_HLEN'
    condition made sense.
    However there's no such guarantee in the generic 'skb_vlan_pop'.
    
    For short packets received in rx path going through 'skb_vlan_pop',
    this causes 'skb_vlan_pop' to fail pop-ing a valid vlan hdr (in the non
    hw-accel case) or to fail moving next tag into hw-accel tag.
    
    Remove the 'skb->len < VLAN_ETH_HLEN' condition entirely:
    It is superfluous since inner '__skb_vlan_pop' already verifies there
    are VLAN_ETH_HLEN writable bytes at the mac_header.
    
    Note this presents a slight change to skb_vlan_pop() users:
    In case total length is smaller than VLAN_ETH_HLEN, skb_vlan_pop() now
    returns an error, as opposed to previous "no-op" behavior.
    Existing callers (e.g. tc act vlan, ovs) usually drop the packet if
    'skb_vlan_pop' fails.
    
    Fixes: 93515d53 ("net: move vlan pop/push functions into common code")
    Signed-off-by: default avatarShmulik Ladkani <shmulik.ladkani@gmail.com>
    Cc: Pravin Shelar <pshelar@ovn.org>
    Reviewed-by: default avatarPravin B Shelar <pshelar@ovn.org>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    636c2628
skbuff.c 121 KB