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Subject[PATCH 4.19 10/89] 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
@@ -505,19 +505,21 @@ 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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