From: William Tu <u9012063@gmail.com>
Date: Wed, 2 Aug 2017 08:43:52 -0700
Subject: bpf: fix the printing of ifindex
Patch-mainline: v4.14-rc1
Git-commit: eb48d682814c8b0e44111c45d7c554e1989fd10d
References: bsc#1109837

Save the ifindex before it gets zeroed so the invalid
ifindex can be printed out.

Signed-off-by: William Tu <u9012063@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/core/filter.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2509,15 +2509,16 @@ int xdp_do_redirect(struct net_device *d
 {
 	struct redirect_info *ri = this_cpu_ptr(&redirect_info);
 	struct net_device *fwd;
+	u32 index = ri->ifindex;
 
 	if (ri->map)
 		return xdp_do_redirect_map(dev, xdp, xdp_prog);
 
-	fwd = dev_get_by_index_rcu(dev_net(dev), ri->ifindex);
+	fwd = dev_get_by_index_rcu(dev_net(dev), index);
 	ri->ifindex = 0;
 	ri->map = NULL;
 	if (unlikely(!fwd)) {
-		bpf_warn_invalid_xdp_redirect(ri->ifindex);
+		bpf_warn_invalid_xdp_redirect(index);
 		return -EINVAL;
 	}
 
@@ -2531,11 +2532,12 @@ int xdp_do_generic_redirect(struct net_d
 {
 	struct redirect_info *ri = this_cpu_ptr(&redirect_info);
 	unsigned int len;
+	u32 index = ri->ifindex;
 
-	dev = dev_get_by_index_rcu(dev_net(dev), ri->ifindex);
+	dev = dev_get_by_index_rcu(dev_net(dev), index);
 	ri->ifindex = 0;
 	if (unlikely(!dev)) {
-		bpf_warn_invalid_xdp_redirect(ri->ifindex);
+		bpf_warn_invalid_xdp_redirect(index);
 		goto err;
 	}