Re: [bug report] selftest: bpf: Test bpf_sk_assign_tcp_reqsk().

[Dan Carpenter <dan.carpenter@linaro.org>]

On Mon, Aug 19, 2024 at 09:54:00PM +0300, Dan Carpenter wrote:
> Hello Kuniyuki Iwashima,
> 
> Commit a74712241b46 ("selftest: bpf: Test
> bpf_sk_assign_tcp_reqsk().") from Jan 15, 2024 (linux-next), leads to
> the following Smatch static checker warning:
> 
> 	tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c:493 tcp_validate_cookie()
> 	warn: off by one 'mssind' == ARRAY_SIZE()?
> 
> ./tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c
>     462 static int tcp_validate_cookie(struct tcp_syncookie *ctx)
>     463 {
>     464         u32 cookie = bpf_ntohl(ctx->tcp->ack_seq) - 1;
>     465         u32 seq = bpf_ntohl(ctx->tcp->seq) - 1;
>     466         u64 first = 0, second;
>     467         int mssind;
>     468         u32 hash;
>     469 
>     470         if (ctx->ipv4)
>     471                 first = (u64)ctx->ipv4->saddr << 32 | ctx->ipv4->daddr;
>     472         else if (ctx->ipv6)
>     473                 first = (u64)ctx->ipv6->saddr.in6_u.u6_addr8[0] << 32 |
>     474                         ctx->ipv6->daddr.in6_u.u6_addr32[0];
>     475 
>     476         second = (u64)seq << 32 | ctx->tcp->source << 16 | ctx->tcp->dest;
>     477         hash = siphash_2u64(first, second, &test_key_siphash);
>     478 
>     479         if (ctx->attrs.tstamp_ok)
>     480                 hash -= ctx->attrs.rcv_tsecr & COOKIE_MASK;
>     481         else
>     482                 hash &= ~COOKIE_MASK;
>     483 
>     484         hash -= cookie & ~COOKIE_MASK;
>     485         if (hash)
>     486                 goto err;
>     487 
>     488         mssind = (cookie & (3 << 6)) >> 6;
>     489         if (ctx->ipv4) {
>     490                 if (mssind > ARRAY_SIZE(msstab4))
>                                    ^
> Should be >= instead of >.
> 
>     491                         goto err;
>     492 
> --> 493                 ctx->attrs.mss = msstab4[mssind];
>     494         } else {
>     495                 if (mssind > ARRAY_SIZE(msstab6))
                                     ^

Here too, I guess.

regards,
dan carpenter