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>
This commit is contained in:
Stanislav Fomichev 2019-04-01 13:57:32 -07:00 committed by Daniel Borkmann
parent 822fe61795
commit b9e9c8599f

View File

@ -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);