linux-kernel - Re: [v2 PATCH bpf-next 1/2] bpf: Check percpu map value size first

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Message-ID: <a82347fb-717b-48d8-8b8f-c62ac6b95929@gmail.com>
Date: Tue, 10 Sep 2024 10:35:51 +0800
From: Tao Chen <chen.dylane@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Hou Tao <houtao1@...wei.com>, Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, bpf@...r.kernel.org,
 linux-kernel@...r.kernel.org, jinke han <jinkehan@...iglobal.com>
Subject: Re: [v2 PATCH bpf-next 1/2] bpf: Check percpu map value size first

在 2024/9/10 04:17, Andrii Nakryiko 写道:
> On Mon, Sep 9, 2024 at 12:14 AM Tao Chen <chen.dylane@...il.com> wrote:
>>
>> Percpu map is often used, but the map value size limit often ignored,
>> like issue: https://github.com/iovisor/bcc/issues/2519. Actually,
>> percpu map value size is bound by PCPU_MIN_UNIT_SIZE, so we
>> can check the value size whether it exceeds PCPU_MIN_UNIT_SIZE first,
>> like percpu map of local_storage. Maybe the error message seems clearer
>> compared with "cannot allocate memory".
>>
>> Signed-off-by: Tao Chen <chen.dylane@...il.com>
>> Signed-off-by: jinke han <jinkehan@...iglobal.com>
> 
> names in SOB should be capitalized

Hi Andrii，thank you for your attention, i will change it.

> 
> the check is useful, so:
> 
> Acked-by: Andrii Nakryiko <andrii@...nel.org>
> 
>> ---
>>   kernel/bpf/arraymap.c | 3 +++
>>   kernel/bpf/hashtab.c  | 3 +++
>>   2 files changed, 6 insertions(+)
>>
>> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
>> index a43e62e2a8bb..79660e3fca4c 100644
>> --- a/kernel/bpf/arraymap.c
>> +++ b/kernel/bpf/arraymap.c
>> @@ -73,6 +73,9 @@ int array_map_alloc_check(union bpf_attr *attr)
>>          /* avoid overflow on round_up(map->value_size) */
>>          if (attr->value_size > INT_MAX)
>>                  return -E2BIG;
>> +       /* percpu map value size is bound by PCPU_MIN_UNIT_SIZE */
>> +       if (percpu && round_up(attr->value_size, 8) > PCPU_MIN_UNIT_SIZE)
>> +               return -E2BIG;
>>
>>          return 0;
>>   }
>> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
>> index 45c7195b65ba..b14b87463ee0 100644
>> --- a/kernel/bpf/hashtab.c
>> +++ b/kernel/bpf/hashtab.c
>> @@ -462,6 +462,9 @@ static int htab_map_alloc_check(union bpf_attr *attr)
>>                   * kmalloc-able later in htab_map_update_elem()
>>                   */
>>                  return -E2BIG;
>> +       /* percpu map value size is bound by PCPU_MIN_UNIT_SIZE */
>> +       if (percpu && round_up(attr->value_size, 8) > PCPU_MIN_UNIT_SIZE)
>> +               return -E2BIG;
>>
>>          return 0;
>>   }
>> --
>> 2.25.1
>>


-- 
Best Regards
Dylane Chen