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>
Signed-off-by: Chatur27 <jasonbright2709@gmail.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index faffcd8438a2..f5669da0e8f7 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2305,6 +2305,8 @@ void synchronize_net(void);
 int init_dummy_netdev(struct net_device *dev);
 
 DECLARE_PER_CPU(int, xmit_recursion);
+#define XMIT_RECURSION_LIMIT	10
+
 static inline int dev_recursion_level(void)
 {
 	return this_cpu_read(xmit_recursion);