From: Kui-Feng Lee <sinquersw@gmail.com>
To: Eduard Zingerman <eddyz87@gmail.com>,
Kui-Feng Lee <thinker.li@gmail.com>,
bpf@vger.kernel.org, ast@kernel.org, martin.lau@linux.dev,
song@kernel.org, kernel-team@meta.com, andrii@kernel.org
Cc: kuifeng@meta.com
Subject: Re: [PATCH bpf-next 07/11] bpf: check_map_access() with the knowledge of arrays.
Date: Fri, 12 Apr 2024 12:29:16 -0700 [thread overview]
Message-ID: <79781f94-11b2-452e-8a3e-0ac3cf455166@gmail.com> (raw)
In-Reply-To: <520f62bee1e1a037c53dafabf4c4b71adee71cd2.camel@gmail.com>
On 4/12/24 12:08, Eduard Zingerman wrote:
> On Fri, 2024-04-12 at 09:32 -0700, Kui-Feng Lee wrote:
>>
>> On 4/11/24 15:14, Eduard Zingerman wrote:
>>> On Tue, 2024-04-09 at 17:41 -0700, Kui-Feng Lee wrote:
>>> [...]
>>>
>>>> Any access to elements other than the first one would be rejected.
>>>
>>> I'm not sure this is true, could you please point me to a specific
>>> check in the code that enforces access to go to the first element?
>>> The check added in this patch only enforces correct alignment with
>>> array element start.
>>
>> I mean accessing to elements other than the first one would be rejected
>> if we don't have this patch.
>
> Oh, I misunderstood the above statement then.
> The way I read it was: "after this patch access to elements other than
> the first one would be rejected". While this patch explicitly allows
> access to the subsequent array elements, hence confusion.
> Sorry for the noise.
I will rephrase it to make it more clear.
>
>>
>> Before the change, it enforces correct alignment with the start of the
>> whole array. Once the array feature is enabled, the "size" of struct
>> btf_field will be the size of entire array. In another word, accessing
>> to later elements, other than the first one, doesn't align with the
>> beginning of entire array, and will be rejected.
>
next prev parent reply other threads:[~2024-04-12 19:29 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-10 0:41 [PATCH bpf-next 00/11] Enable BPF programs to declare arrays of kptr, bpf_rb_root, and bpf_list_head Kui-Feng Lee
2024-04-10 0:41 ` [PATCH bpf-next 01/11] bpf: Remove unnecessary checks on the offset of btf_field Kui-Feng Lee
2024-04-11 22:12 ` Eduard Zingerman
2024-04-10 0:41 ` [PATCH bpf-next 02/11] bpf: Remove unnecessary call to btf_field_type_size() Kui-Feng Lee
2024-04-11 22:12 ` Eduard Zingerman
2024-04-10 0:41 ` [PATCH bpf-next 03/11] bpf: Add nelems to struct btf_field_info and btf_field Kui-Feng Lee
2024-04-10 0:41 ` [PATCH bpf-next 04/11] bpf: check_map_kptr_access() compute the offset from the reg state Kui-Feng Lee
2024-04-11 22:13 ` Eduard Zingerman
2024-04-12 4:00 ` Kui-Feng Lee
2024-04-10 0:41 ` [PATCH bpf-next 05/11] bpf: initialize/free array of btf_field(s) Kui-Feng Lee
2024-04-11 22:13 ` Eduard Zingerman
2024-04-12 3:56 ` Kui-Feng Lee
2024-04-12 15:32 ` Eduard Zingerman
2024-04-12 17:00 ` Kui-Feng Lee
2024-04-10 0:41 ` [PATCH bpf-next 06/11] bpf: Find btf_field with the knowledge of arrays Kui-Feng Lee
2024-04-11 22:14 ` Eduard Zingerman
2024-04-12 2:00 ` Kui-Feng Lee
2024-04-10 0:41 ` [PATCH bpf-next 07/11] bpf: check_map_access() " Kui-Feng Lee
2024-04-11 22:14 ` Eduard Zingerman
2024-04-12 16:32 ` Kui-Feng Lee
2024-04-12 19:08 ` Eduard Zingerman
2024-04-12 19:29 ` Kui-Feng Lee [this message]
2024-04-12 19:50 ` Eduard Zingerman
2024-04-10 0:41 ` [PATCH bpf-next 08/11] bpf: Enable and verify btf_field arrays Kui-Feng Lee
2024-04-10 0:41 ` [PATCH bpf-next 09/11] selftests/bpf: Test global kptr arrays Kui-Feng Lee
2024-04-10 0:41 ` [PATCH bpf-next 10/11] selftests/bpf: Test global bpf_rb_root arrays Kui-Feng Lee
2024-04-10 0:41 ` [PATCH bpf-next 11/11] selftests/bpf: Test global bpf_list_head arrays Kui-Feng Lee
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