bpf: enforce recursion limit on redirects
Respect the stack's xmit_recursion limit for calls into dev_queue_xmit().
Currently, they are not handeled by the limiter when attached to clsact's
egress parent, for example, and a buggy program redirecting it to the
same device again could run into stack overflow eventually. It would be
good if we could notify an admin to give him a chance to react. We reuse
xmit_recursion instead of having one private to eBPF, so that the stack's
current recursion depth will be taken into account as well. Follow-up to
commit 3896d655f4d4 ("bpf: introduce bpf_clone_redirect() helper") and
27b29f63058d ("bpf: add bpf_redirect() helper").
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index c43c9d2..b148357 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3144,8 +3144,6 @@
DEFINE_PER_CPU(int, xmit_recursion);
EXPORT_SYMBOL(xmit_recursion);
-#define RECURSION_LIMIT 10
-
/**
* dev_loopback_xmit - loop back @skb
* @net: network namespace this loopback is happening in
@@ -3388,8 +3386,8 @@
int cpu = smp_processor_id(); /* ok because BHs are off */
if (txq->xmit_lock_owner != cpu) {
-
- if (__this_cpu_read(xmit_recursion) > RECURSION_LIMIT)
+ if (unlikely(__this_cpu_read(xmit_recursion) >
+ XMIT_RECURSION_LIMIT))
goto recursion_alert;
skb = validate_xmit_skb(skb, dev);