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    Subject[PATCH 5.4 012/123] ipvlan: dont deref eth hdr before checking its set
    Date
    From: Mahesh Bandewar <maheshb@google.com>

    [ Upstream commit ad8192767c9f9cf97da57b9ffcea70fb100febef ]

    IPvlan in L3 mode discards outbound multicast packets but performs
    the check before ensuring the ether-header is set or not. This is
    an error that Eric found through code browsing.

    Fixes: 2ad7bf363841 (“ipvlan: Initial check-in of the IPVLAN driver.”)
    Signed-off-by: Mahesh Bandewar <maheshb@google.com>
    Reported-by: Eric Dumazet <edumazet@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/net/ipvlan/ipvlan_core.c | 18 ++++++++++--------
    1 file changed, 10 insertions(+), 8 deletions(-)

    --- a/drivers/net/ipvlan/ipvlan_core.c
    +++ b/drivers/net/ipvlan/ipvlan_core.c
    @@ -499,19 +499,21 @@ static int ipvlan_process_outbound(struc
    struct ethhdr *ethh = eth_hdr(skb);
    int ret = NET_XMIT_DROP;

    - /* In this mode we dont care about multicast and broadcast traffic */
    - if (is_multicast_ether_addr(ethh->h_dest)) {
    - pr_debug_ratelimited("Dropped {multi|broad}cast of type=[%x]\n",
    - ntohs(skb->protocol));
    - kfree_skb(skb);
    - goto out;
    - }
    -
    /* The ipvlan is a pseudo-L2 device, so the packets that we receive
    * will have L2; which need to discarded and processed further
    * in the net-ns of the main-device.
    */
    if (skb_mac_header_was_set(skb)) {
    + /* In this mode we dont care about
    + * multicast and broadcast traffic */
    + if (is_multicast_ether_addr(ethh->h_dest)) {
    + pr_debug_ratelimited(
    + "Dropped {multi|broad}cast of type=[%x]\n",
    + ntohs(skb->protocol));
    + kfree_skb(skb);
    + goto out;
    + }
    +
    skb_pull(skb, sizeof(*ethh));
    skb->mac_header = (typeof(skb->mac_header))~0U;
    skb_reset_network_header(skb);

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