From: Eduard Zingerman <eddyz87@gmail.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
bpf@vger.kernel.org, daniel@iogearbox.net,
martin.lau@kernel.org, kernel-team@meta.com
Subject: Re: [PATCH v3 bpf-next 03/10] bpf: fix check for attempt to corrupt spilled pointer
Date: Tue, 05 Dec 2023 15:34:43 +0200 [thread overview]
Message-ID: <7aa8af01db4fdcbedab376423d3960c22016aba3.camel@gmail.com> (raw)
In-Reply-To: <CAEf4Bzb8LouFSSX5DED_ucgq_xuhukE1BQ7y=hxY0c17Nq4T+Q@mail.gmail.com>
On Mon, 2023-12-04 at 19:56 -0800, Andrii Nakryiko wrote:
[...]
> > > So it makes me feel like the intent was to reject any partial writes
> > > with spilled reg slots. We could probably improve that to just make
> > > sure that we don't turn spilled pointers into STACK_MISC in unpriv,
> > > but I'm not sure if it's worth doing that instead of keeping things
> > > simple?
> >
> > You mean like below?
> >
> > if (!env->allow_ptr_leaks &&
> > is_spilled_reg(&state->stack[spi]) &&
> > is_spillable_regtype(state->stack[spi].spilled_ptr.type) &&
>
> Honestly, I wouldn't trust is_spillable_regtype() the way it's
> written, it's too easy to forget to add a new register type to the
> list. I think the only "safe to spill" register is probably
> SCALAR_VALUE, so I'd just do `type != SCALAR_VALUE`.
>
> But yes, I think that's the right approach.
'type != SCALAR_VALUE' makes sense as well.
Do you plan to add this check as a part of current patch?
> If we were being pedantic, though, we'd need to take into account
> offset and see if [offset, offset + size) overlaps with any
> STACK_SPILL/STACK_DYNPTR/STACK_ITER slots.
>
> But tbh, given it's unpriv programs we are talking about, I probably
> wouldn't bother extending this logic too much.
Yes, that's definitely is an ommission.
next prev parent reply other threads:[~2023-12-05 13:34 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-04 19:25 [PATCH v3 bpf-next 00/10] Complete BPF verifier precision tracking support for register spills Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 01/10] bpf: support non-r10 register spill/fill to/from stack in precision tracking Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 02/10] selftests/bpf: add stack access precision test Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 03/10] bpf: fix check for attempt to corrupt spilled pointer Andrii Nakryiko
2023-12-04 22:12 ` Eduard Zingerman
2023-12-04 22:15 ` Eduard Zingerman
2023-12-05 0:23 ` Andrii Nakryiko
2023-12-05 0:54 ` Eduard Zingerman
2023-12-05 3:56 ` Andrii Nakryiko
2023-12-05 13:34 ` Eduard Zingerman [this message]
2023-12-05 18:30 ` Andrii Nakryiko
2023-12-05 18:49 ` Eduard Zingerman
2023-12-05 18:55 ` Andrii Nakryiko
2023-12-05 1:45 ` Alexei Starovoitov
2023-12-05 3:50 ` Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 04/10] bpf: preserve STACK_ZERO slots on partial reg spills Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 05/10] selftests/bpf: validate STACK_ZERO is preserved on subreg spill Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 06/10] bpf: preserve constant zero when doing partial register restore Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 07/10] selftests/bpf: validate zero preservation for sub-slot loads Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 08/10] bpf: track aligned STACK_ZERO cases as imprecise spilled registers Andrii Nakryiko
2023-12-04 19:26 ` [PATCH v3 bpf-next 09/10] selftests/bpf: validate precision logic in partial_stack_load_preserves_zeros Andrii Nakryiko
2023-12-04 19:26 ` [PATCH v3 bpf-next 10/10] bpf: use common instruction history across all states Andrii Nakryiko
2023-12-04 22:32 ` [PATCH v3 bpf-next 00/10] Complete BPF verifier precision tracking support for register spills Andrii Nakryiko
2023-12-04 23:02 ` Yonghong Song
2023-12-04 23:52 ` Andrii Nakryiko
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