[PATCH net-next] bpf: fix the printing of ifindex

[William Tu <u9012063@gmail.com>]

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

Signed-off-by: William Tu <u9012063@gmail.com>
---
 net/core/filter.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 7e9708653c6f..78d00933dbe7 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2509,15 +2509,16 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
 {
 	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_device *dev, struct sk_buff *skb)
 {
 	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;
 	}
 
-- 
2.7.4