netfilter: allow hooks to pass error code back up the stack

SELinux would like to pass certain fatal errors back up the stack.  This patch
implements the generic netfilter support for this functionality.

Based-on-patch-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 2 deletions

diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index 85dabb86be6f..32fcbe290c04 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -173,9 +173,11 @@ next_hook:
                              outdev, &elem, okfn, hook_thresh);
         if (verdict == NF_ACCEPT || verdict == NF_STOP) {
                 ret = 1;
-        } else if (verdict == NF_DROP) {
+        } else if ((verdict & NF_VERDICT_MASK) == NF_DROP) {
                 kfree_skb(skb);
-                ret = -EPERM;
+                ret = -(verdict >> NF_VERDICT_BITS);
+                if (ret == 0)
+                        ret = -EPERM;
         } else if ((verdict & NF_VERDICT_MASK) == NF_QUEUE) {
                 if (!nf_queue(skb, elem, pf, hook, indev, outdev, okfn,
                               verdict >> NF_VERDICT_BITS))