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From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Andrii Nakryiko <andrii@kernel.org>, bpf <bpf@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH bpf-next 03/13] libbpf: prevent UBSan from complaining about integer overflow
Date: Thu, 25 Nov 2021 17:23:11 -0800	[thread overview]
Message-ID: <CAEf4BzZ5AEJHr9p0zBn6A=-EAkMhToVdjLx7eijXsJYeyX2_rg@mail.gmail.com> (raw)
In-Reply-To: <8350db18-6e13-66da-220c-c1e53562326e@iogearbox.net>

On Thu, Nov 25, 2021 at 3:19 PM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 11/25/21 11:21 PM, Daniel Borkmann wrote:
> > On 11/24/21 1:23 AM, Andrii Nakryiko wrote:
> >> Integer overflow is intentional, silence the sanitizer. It works
> >> completely reliably on sane compilers and architectures.
> >>
> >> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
> >> ---
> >>   tools/lib/bpf/btf.c | 1 +
> >>   1 file changed, 1 insertion(+)
> >>
> >> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> >> index 8024fe355ca8..be1dafd56a13 100644
> >> --- a/tools/lib/bpf/btf.c
> >> +++ b/tools/lib/bpf/btf.c
> >> @@ -3127,6 +3127,7 @@ struct btf_dedup {
> >>       struct strset *strs_set;
> >>   };
> >> +__attribute__((no_sanitize("signed-integer-overflow")))
> >>   static long hash_combine(long h, long value)
> >>   {
> >>       return h * 31 + value;
> >>
> >
> > Sgtm, I guess my only question, was there a reason for not using e.g. __u64 in
> > the first place? Meaning, __u64 hash_combine(__u64 h, __u64 value) plus the
> > call-sites where you have h variable re-feeding into hash_combine().
>
> Given the remainder of the series is all straight forward, I took that in already,
> but would still be nice if we can silence the sanitizer complaint w/o such attribute
> workaround.

You are right, I'll follow up with u64 conversion and will drop the attribute.

>
> Thanks,
> Daniel

  reply	other threads:[~2021-11-26  1:25 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-24  0:23 [PATCH bpf-next 00/13] Fix sanitizer-reported libbpf and selftest issues Andrii Nakryiko
2021-11-24  0:23 ` [PATCH bpf-next 01/13] tools/resolve_btf_ids: close ELF file on error Andrii Nakryiko
2021-11-24  0:23 ` [PATCH bpf-next 02/13] libbpf: fix potential misaligned memory access in btf_ext__new() Andrii Nakryiko
2021-11-24  0:23 ` [PATCH bpf-next 03/13] libbpf: prevent UBSan from complaining about integer overflow Andrii Nakryiko
2021-11-25 22:21   ` Daniel Borkmann
2021-11-25 23:19     ` Daniel Borkmann
2021-11-26  1:23       ` Andrii Nakryiko [this message]
2021-11-24  0:23 ` [PATCH bpf-next 04/13] libbpf: don't call libc APIs with NULL pointers Andrii Nakryiko
2021-11-24  0:23 ` [PATCH bpf-next 05/13] libbpf: fix glob_syms memory leak in bpf_linker Andrii Nakryiko
2021-11-24  0:23 ` [PATCH bpf-next 06/13] libbpf: fix using invalidated memory " Andrii Nakryiko
2021-11-24  0:23 ` [PATCH bpf-next 07/13] selftests/bpf: fix UBSan complaint about signed __int128 overflow Andrii Nakryiko
2021-11-24  0:23 ` [PATCH bpf-next 08/13] selftests/bpf: fix possible NULL passed to memcpy() with zero size Andrii Nakryiko
2021-11-24  0:23 ` [PATCH bpf-next 09/13] selftests/bpf: prevent misaligned memory access in get_stack_raw_tp test Andrii Nakryiko
2021-11-24  0:23 ` [PATCH bpf-next 10/13] selftests/bpf: fix misaligned memory access in queue_stack_map test Andrii Nakryiko
2021-11-24  0:23 ` [PATCH bpf-next 11/13] selftests/bpf: prevent out-of-bounds stack access in test_bpffs Andrii Nakryiko
2021-11-24  0:23 ` [PATCH bpf-next 12/13] selftests/bpf: fix misaligned memory accesses in xdp_bonding test Andrii Nakryiko
2021-11-24  0:23 ` [PATCH bpf-next 13/13] selftests/bpf: fix misaligned accesses in xdp and xdp_bpf2bpf tests Andrii Nakryiko

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