From b9e9c8599f0f23e3d2051befc9966a84b639f64f Mon Sep 17 00:00:00 2001 From: Stanislav Fomichev <sdf@google.com> Date: Mon, 1 Apr 2019 13:57:32 -0700 Subject: [PATCH] flow_dissector: fix clamping of BPF flow_keys for non-zero nhoff Don't allow BPF program to set flow_keys->nhoff to less than initial value. We currently don't read the value afterwards in anything but the tests, but it's still a good practice to return consistent values to the test programs. Signed-off-by: Stanislav Fomichev <sdf@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> --- net/core/flow_dissector.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c index 9b84250039df1..94a450b2191a9 100644 --- a/net/core/flow_dissector.c +++ b/net/core/flow_dissector.c @@ -717,7 +717,8 @@ bool __skb_flow_bpf_dissect(struct bpf_prog *prog, /* Restore state */ memcpy(cb, &cb_saved, sizeof(cb_saved)); - flow_keys->nhoff = clamp_t(u16, flow_keys->nhoff, 0, skb->len); + flow_keys->nhoff = clamp_t(u16, flow_keys->nhoff, + skb_network_offset(skb), skb->len); flow_keys->thoff = clamp_t(u16, flow_keys->thoff, flow_keys->nhoff, skb->len); -- GitLab