Re: [RFC PATCH bpf-next v2 4/6] bpf: Add common attr support for map_create

[Leon Hwang <leon.hwang@linux.dev>]

On 2025/9/18 05:49, Alexei Starovoitov wrote:
> On Wed, Sep 17, 2025 at 2:39 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
>>
>> On Thu, Sep 11, 2025 at 9:33 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>>>

[...]

>>>
>>> +       if (common_attrs->log_buf) {
>>> +               log = kvzalloc(sizeof(*log), GFP_KERNEL);
>>> +               if (!log)
>>> +                       return -ENOMEM;
>>> +               err = bpf_vlog_init(log, BPF_LOG_FIXED, u64_to_user_ptr(common_attrs->log_buf),
>>> +                                   common_attrs->log_size, NULL);
>>> +               if (err) {
>>> +                       kvfree(log);
>>> +                       return err;
>>> +               }
>>> +       }
>>
>> what if we keep bpf_verifier_log on stack? It's 1KB, should be still
>> fine to be on kernel stack, no?
>
> 1k is a lot. I'm pretty nervous about stack usage. kmalloc is cheap.
> Let's use it. I'd drop 'v' part. There is no way it will fallback
> to valloc() even if we double BPF_VERIFIER_TMP_LOG_SIZE in the future.

I'll drop 'v' part in the next revision.

Thanks,
Leon