FAILED: patch "[PATCH] vrf: Reset IPCB/IP6CB when processing outbound pkts in vrf" failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ee201011c1e1563c114a55c86eb164b236f18e84 Mon Sep 17 00:00:00 2001
From: Stephen Suryaputra <[email protected]>
Date: Tue, 30 Nov 2021 11:26:37 -0500
Subject: [PATCH] vrf: Reset IPCB/IP6CB when processing outbound pkts in vrf
dev xmit

IPCB/IP6CB need to be initialized when processing outbound v4 or v6 pkts in the codepath of vrf device xmit function so that leftover garbage doesn't cause futher code that uses the CB to incorrectly process the pkt.

One occasion of the issue might occur when MPLS route uses the vrf device as the outgoing device such as when the route is added using "ip -f mpls route add <label> dev <vrf>" command.

The problems seems to exist since day one. Hence I put the day one commits on the Fixes tags.

index ccf677015d5b..131c745dc701 100644
@@ -497,6 +497,7 @@ static netdev_tx_t vrf_process_v6_outbound(struct sk_buff *skb,
 	/* strip the ethernet header added for pass through VRF device */
 	__skb_pull(skb, skb_network_offset(skb));
 
+	memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
 	ret = vrf_ip6_local_out(net, skb->sk, skb);
 	if (unlikely(net_xmit_eval(ret)))
 		dev->stats.tx_errors++;

@@ -579,6 +580,7 @@ static netdev_tx_t vrf_process_v4_outbound(struct sk_buff *skb,
 					       RT_SCOPE_LINK);
 	}
 
+	memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
 	ret = vrf_ip_local_out(dev_net(skb_dst(skb)->dev), skb->sk, skb);
 	if (unlikely(net_xmit_eval(ret)))
 		vrf_dev->stats.tx_errors++;

This patch is not needed in 4.4.

Why not? The two "Fixes:" tag show that those commits are in 4.4:

193125dbd8eb showed up in 4.3, and 35402e313663 showed up in 4.4.

so why isn't this needed in 4.4.y?

thanks,

greg k-h

The patch fixes a corner case with MPLS + VRF. The VRF feature is not really usable before 4.9; I doubt VRF + MPLS with a last label pop is usable in 4.4.

Ok, thanks for the explaination.

greg k-h