bpf: Use ARG_CONST_SIZE_OR_ZERO for 3rd argument of bpf_tcp_raw_gen_syncookie_ipv...

These functions already check that th_len < sizeof(*th), and
propagating the lower bound (th_len > 0) may be challenging
in complex code, e.g. as is the case with xdp_synproxy test on
s390x [1]. Switch to ARG_CONST_SIZE_OR_ZERO in order to make the
verifier accept code where it cannot prove that th_len > 0.

[1] https://lore.kernel.org/bpf/CAEf4Bzb3uiSHtUbgVWmkWuJ5Sw1UZd4c_iuS4QXtUkXmTTtXuQ@mail.gmail.com/

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20230128000650.1516334-2-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/net/core/filter.c b/net/core/filter.c
index d8f9b53..0039cf1 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7536,7 +7536,7 @@ static const struct bpf_func_proto bpf_tcp_raw_gen_syncookie_ipv4_proto = {
        .arg1_type      = ARG_PTR_TO_FIXED_SIZE_MEM,
        .arg1_size      = sizeof(struct iphdr),
        .arg2_type      = ARG_PTR_TO_MEM,
-       .arg3_type      = ARG_CONST_SIZE,
+       .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 };
 
 BPF_CALL_3(bpf_tcp_raw_gen_syncookie_ipv6, struct ipv6hdr *, iph,
@@ -7568,7 +7568,7 @@ static const struct bpf_func_proto bpf_tcp_raw_gen_syncookie_ipv6_proto = {
        .arg1_type      = ARG_PTR_TO_FIXED_SIZE_MEM,
        .arg1_size      = sizeof(struct ipv6hdr),
        .arg2_type      = ARG_PTR_TO_MEM,
-       .arg3_type      = ARG_CONST_SIZE,
+       .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 };
 
 BPF_CALL_2(bpf_tcp_raw_check_syncookie_ipv4, struct iphdr *, iph,