From: Eduard Zingerman <eddyz87@gmail.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Xu Kuohai <xukuohai@huaweicloud.com>,
Edward Cree <ecree.xilinx@gmail.com>
Cc: Yonghong Song <yonghong.song@linux.dev>,
bpf@vger.kernel.org, netdev@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kselftest@vger.kernel.org,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Matt Bobrowski <mattbobrowski@google.com>,
Brendan Jackman <jackmanb@chromium.org>,
Paul Moore <paul@paul-moore.com>,
James Morris <jmorris@namei.org>,
"Serge E . Hallyn" <serge@hallyn.com>,
Khadija Kamran <kamrankhadijadj@gmail.com>,
Casey Schaufler <casey@schaufler-ca.com>,
Ondrej Mosnacek <omosnace@redhat.com>,
Kees Cook <keescook@chromium.org>,
John Johansen <john.johansen@canonical.com>,
Lukas Bulwahn <lukas.bulwahn@gmail.com>,
Roberto Sassu <roberto.sassu@huawei.com>,
Shung-Hsi Yu <shung-hsi.yu@suse.com>
Subject: Re: [PATCH bpf-next v3 07/11] bpf: Fix a false rejection caused by AND operation
Date: Mon, 29 Apr 2024 15:18:25 -0700 [thread overview]
Message-ID: <7cf8b58011156af99816391d3afd5c52e48ea8b7.camel@gmail.com> (raw)
In-Reply-To: <CAEf4BzZb38EemdD8ahX4Px3vWCp=ani6vcX71Z-1_MLeATNjwQ@mail.gmail.com>
On Mon, 2024-04-29 at 13:58 -0700, Andrii Nakryiko wrote:
[...]
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 8f0f2e21699e..b69c89bc5cfc 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -13478,6 +13478,28 @@ static void scalar32_min_max_and(struct bpf_reg_state *dst_reg,
> > return;
> > }
> >
> > + /* Special case: dst_reg is in range [-1, 0] */
> > + if (dst_reg->s32_min_value == -1 && dst_reg->s32_max_value == 0) {
> > + var32_off = tnum_union(src_reg->var_off, tnum_const(0));
> > + dst_reg->var_off = tnum_with_subreg(dst_reg->var_off, var32_off);
> > + dst_reg->u32_min_value = var32_off.value;
> > + dst_reg->u32_max_value = min(dst_reg->u32_max_value, umax_val);
>
> can you explain the logic behing u32 min/max updates, especially that
> we use completely different values for min/max and it's not clear why
> u32_min <= u32_max invariant will always hold. Same below
I agree with Andrii here.
It appears that dst_reg.{min,max} fields should be set as
{min(src.min, 0), max(src.max, 0)} for both signed and unsigned cases.
Wdyt?
>
> > + dst_reg->s32_min_value = min_t(s32, src_reg->s32_min_value, 0);
> > + dst_reg->s32_max_value = max_t(s32, src_reg->s32_max_value, 0);
> > + return;
> > + }
> > +
> > + /* Special case: src_reg is in range [-1, 0] */
> > + if (src_reg->s32_min_value == -1 && src_reg->s32_max_value == 0) {
> > + var32_off = tnum_union(dst_reg->var_off, tnum_const(0));
> > + dst_reg->var_off = tnum_with_subreg(dst_reg->var_off, var32_off);
> > + dst_reg->u32_min_value = var32_off.value;
> > + dst_reg->u32_max_value = min(dst_reg->u32_max_value, umax_val);
> > + dst_reg->s32_min_value = min_t(s32, dst_reg->s32_min_value, 0);
> > + dst_reg->s32_max_value = max_t(s32, dst_reg->s32_max_value, 0);
> > + return;
> > + }
> > +
> > /* We get our minimum from the var_off, since that's inherently
> > * bitwise. Our maximum is the minimum of the operands' maxima.
> > */
[...]
next prev parent reply other threads:[~2024-04-29 22:18 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-11 12:27 [PATCH bpf-next v3 00/11] Add check for bpf lsm return value Xu Kuohai
2024-04-11 12:27 ` [PATCH bpf-next v3 01/11] bpf, lsm: Annotate lsm hook return value range Xu Kuohai
2024-04-11 12:27 ` [PATCH bpf-next v3 02/11] bpf, lsm: Add helper to read " Xu Kuohai
2024-04-11 12:27 ` [PATCH bpf-next v3 03/11] bpf, lsm: Check bpf lsm hook return values in verifier Xu Kuohai
2024-04-13 11:44 ` Eduard Zingerman
2024-04-11 12:27 ` [PATCH bpf-next v3 04/11] bpf, lsm: Add bpf lsm disabled hook list Xu Kuohai
2024-04-11 12:27 ` [PATCH bpf-next v3 05/11] bpf: Avoid progs for different hooks calling each other with tail call Xu Kuohai
2024-04-11 12:27 ` [PATCH bpf-next v3 06/11] bpf: Fix compare error in function retval_range_within Xu Kuohai
2024-04-12 8:53 ` Shung-Hsi Yu
2024-04-12 8:53 ` [Bpf] " Shung-Hsi Yu
2024-04-25 23:41 ` Andrii Nakryiko
2024-04-26 8:08 ` Xu Kuohai
2024-04-11 12:27 ` [PATCH bpf-next v3 07/11] bpf: Fix a false rejection caused by AND operation Xu Kuohai
2024-04-19 23:00 ` Eduard Zingerman
2024-04-20 8:33 ` Xu Kuohai
2024-04-23 21:55 ` Yonghong Song
2024-04-24 2:25 ` Xu Kuohai
2024-04-24 22:06 ` Yonghong Song
2024-04-25 2:42 ` Xu Kuohai
2024-04-25 16:28 ` Yonghong Song
2024-04-26 7:43 ` Xu Kuohai
2024-04-26 20:36 ` Andrii Nakryiko
2024-04-28 15:15 ` Xu Kuohai
2024-04-29 20:58 ` Andrii Nakryiko
2024-04-29 22:18 ` Eduard Zingerman [this message]
2024-04-30 3:56 ` Xu Kuohai
2024-04-30 3:54 ` Xu Kuohai
2024-04-29 21:56 ` Eduard Zingerman
2024-04-11 12:27 ` [PATCH bpf-next v3 08/11] selftests/bpf: Avoid load failure for token_lsm.c Xu Kuohai
2024-04-11 12:27 ` [PATCH bpf-next v3 09/11] selftests/bpf: Add return value checks for failed tests Xu Kuohai
2024-04-11 12:27 ` [PATCH bpf-next v3 10/11] selftests/bpf: Add test for lsm tail call Xu Kuohai
2024-04-11 12:27 ` [PATCH bpf-next v3 11/11] selftests/bpf: Add verifier tests for bpf lsm Xu Kuohai
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