From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Kees Cook <keescook@chromium.org>
Cc: Yonghong Song <yhs@fb.com>, Dmitry Vyukov <dvyukov@google.com>,
Kurt Manucredo <fuzzybritches0@gmail.com>,
syzbot+bed360704c521841c85d@syzkaller.appspotmail.com,
Andrii Nakryiko <andrii@kernel.org>,
Alexei Starovoitov <ast@kernel.org>, bpf <bpf@vger.kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
"David S. Miller" <davem@davemloft.net>,
Jesper Dangaard Brouer <hawk@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
Martin KaFai Lau <kafai@fb.com>, KP Singh <kpsingh@kernel.org>,
Jakub Kicinski <kuba@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>,
Song Liu <songliubraving@fb.com>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
nathan@kernel.org, Nick Desaulniers <ndesaulniers@google.com>,
Clang-Built-Linux ML <clang-built-linux@googlegroups.com>,
linux-kernel-mentees@lists.linuxfoundation.org,
Shuah Khan <skhan@linuxfoundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Kernel Hardening <kernel-hardening@lists.openwall.com>,
kasan-dev <kasan-dev@googlegroups.com>
Subject: Re: [PATCH v4] bpf: core: fix shift-out-of-bounds in ___bpf_prog_run
Date: Thu, 10 Jun 2021 10:52:37 -0700 [thread overview]
Message-ID: <CAADnVQKMwKYgthoQV4RmGpZm9Hm-=wH3DoaNqs=UZRmJKefwGw@mail.gmail.com> (raw)
In-Reply-To: <202106101002.DF8C7EF@keescook>
On Thu, Jun 10, 2021 at 10:06 AM Kees Cook <keescook@chromium.org> wrote:
>
> > > I guess the main question: what should happen if a bpf program writer
> > > does _not_ use compiler nor check_shl_overflow()?
>
> I think the BPF runtime needs to make such actions defined, instead of
> doing a blind shift. It needs to check the size of the shift explicitly
> when handling the shift instruction.
Such ideas were brought up in the past and rejected.
We're not going to sacrifice performance to make behavior a bit more
'defined'. CPUs are doing it deterministically. It's the C standard
that needs fixing.
> Sure, but the point of UBSAN is to find and alert about undefined
> behavior, so we still need to fix this.
No. The undefined behavior of C standard doesn't need "fixing" most of the time.
next prev parent reply other threads:[~2021-06-10 17:53 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <000000000000c2987605be907e41@google.com>
[not found] ` <20210602212726.7-1-fuzzybritches0@gmail.com>
[not found] ` <YLhd8BL3HGItbXmx@kroah.com>
[not found] ` <87609-531187-curtm@phaethon>
[not found] ` <6a392b66-6f26-4532-d25f-6b09770ce366@fb.com>
[not found] ` <CAADnVQKexxZQw0yK_7rmFOdaYabaFpi2EmF6RGs5bXvFHtUQaA@mail.gmail.com>
2021-06-07 7:38 ` [PATCH v4] bpf: core: fix shift-out-of-bounds in ___bpf_prog_run Dmitry Vyukov
2021-06-09 18:20 ` Kees Cook
2021-06-09 23:40 ` Yonghong Song
2021-06-10 5:32 ` Dmitry Vyukov
2021-06-10 6:06 ` Yonghong Song
2021-06-10 17:06 ` Kees Cook
2021-06-10 17:52 ` Alexei Starovoitov [this message]
2021-06-10 20:00 ` Eric Biggers
2021-06-15 16:42 ` [PATCH v5] " Kurt Manucredo
2021-06-15 18:51 ` Edward Cree
2021-06-15 19:33 ` Eric Biggers
2021-06-15 21:08 ` Daniel Borkmann
2021-06-15 21:32 ` Eric Biggers
2021-06-15 21:38 ` Eric Biggers
2021-06-15 21:54 ` Daniel Borkmann
2021-06-15 22:07 ` Eric Biggers
2021-06-15 22:31 ` Kurt Manucredo
2021-06-17 10:09 ` Daniel Borkmann
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