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

[Daniel Borkmann]

On 08/02/2017 05:43 PM, William Tu wrote:

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

Signed-off-by: William Tu <u9012...@gmail.com>

Acked-by: Daniel Borkmann <dan...@iogearbox.net>

  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;

Unrelated, but setting ri->map to NULL is not really needed here
given we have the ri->map test earlier.

        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;
        }