linux-kernel - Re: [PATCH v5 00/15] extend task comm from 16 to 24 for CONFIG_BASE

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Date:   Thu, 21 Oct 2021 20:52:22 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     keescook@...omium.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, arnaldo.melo@...il.com,
        pmladek@...e.com, peterz@...radead.org, viro@...iv.linux.org.uk,
        valentin.schneider@....com, qiang.zhang@...driver.com,
        robdclark@...omium.org, christian@...uner.io,
        dietmar.eggemann@....com, mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, davem@...emloft.net, kuba@...nel.org,
        ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-perf-users@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, oliver.sang@...el.com, lkp@...el.com
Subject: Re: [PATCH v5 00/15] extend task comm from 16 to 24 for
 CONFIG_BASE_FULL

On Thu, 21 Oct 2021 03:45:07 +0000 Yafang Shao <laoar.shao@...il.com> wrote:

> This patchset changes files among many subsystems. I don't know which
> tree it should be applied to, so I just base it on Linus's tree.

I can do that ;)

> There're many truncated kthreads in the kernel, which may make trouble
> for the user, for example, the user can't get detailed device
> information from the task comm.

That sucked of us.

> This patchset tries to improve this problem fundamentally by extending
> the task comm size from 16 to 24. In order to do that, we have to do
> some cleanups first.

It's at v5 and there's no evidence of review activity?  C'mon, folks!

> 1. Make the copy of task comm always safe no matter what the task
> comm size is. For example,
> 
>   Unsafe                 Safe
>   strlcpy                strscpy_pad
>   strncpy                strscpy_pad
>   bpf_probe_read_kernel  bpf_probe_read_kernel_str
>                          bpf_core_read_str
>                          bpf_get_current_comm
>                          perf_event__prepare_comm
>                          prctl(2)
> 
> 2. Replace the old hard-coded 16 with a new macro TASK_COMM_LEN_16 to
> make it more grepable.
> 
> 3. Extend the task comm size to 24 for CONFIG_BASE_FULL case and keep it
> as 16 for CONFIG_BASE_SMALL.

Is this justified?  How much simpler/more reliable/more maintainable/
would the code be if we were to make CONFIG_BASE_SMALL suffer with the
extra 8 bytes?

> 4. Print a warning if the kthread comm is still truncated.