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bpf: fix error check in bpf_tcp_gen_syncookie 

If a SYN cookie is not issued by tcp_v#_gen_syncookie, then the return
value will be exactly 0, rather than <= 0. Let's change the check to
reflect that, especially since mss is an unsigned value and cannot be
negative.

Fixes: 70d6624431 ("bpf: add bpf_tcp_gen_syncookie helper")
Reported-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Petar Penkov <ppenkov@google.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Petar Penkov 2019-08-27 16:46:22 -07:00 committed by Daniel Borkmann
parent 736a55309d
commit 0741be358d
1 changed files with 1 additions and 1 deletions
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2
net/core/filter.c
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@ -5903,7 +5903,7 @@ BPF_CALL_5(bpf_tcp_gen_syncookie, struct sock *, sk, void *, iph, u32, iph_len,
default: default:
return -EPROTONOSUPPORT; return -EPROTONOSUPPORT;
} }
if (mss <= 0) if (mss == 0)
return -ENOENT; return -ENOENT;
return cookie | ((u64)mss << 32); return cookie | ((u64)mss << 32);