linux-kernel - Re: [PATCH 1/7] fs/exec: make __set_task_comm always set a nul terminated string

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Date:   Thu, 11 Nov 2021 10:58:13 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        netdev <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        "linux-perf-use." <linux-perf-users@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel test robot <oliver.sang@...el.com>,
        kbuild test robot <lkp@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Michal Miroslaw <mirq-linux@...e.qmqm.pl>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Matthew Wilcox <willy@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Petr Mladek <pmladek@...e.com>
Subject: Re: [PATCH 1/7] fs/exec: make __set_task_comm always set a nul
 terminated string

On 10.11.21 10:05, Yafang Shao wrote:
> On Wed, Nov 10, 2021 at 4:28 PM David Hildenbrand <david@...hat.com> wrote:
>>
>> On 08.11.21 09:38, Yafang Shao wrote:
>>> Make sure the string set to task comm is always nul terminated.
>>>
>>
>> strlcpy: "the result is always a valid NUL-terminated string that fits
>> in the buffer"
>>
>> The only difference seems to be that strscpy_pad() pads the remainder
>> with zeroes.
>>
>> Is this description correct and I am missing something important?
>>
> 
> In a earlier version [1], the checkpatch.py found a warning:
> WARNING: Prefer strscpy over strlcpy - see:
> https://lore.kernel.org/r/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@mail.gmail.com/
> So I replaced strlcpy() with strscpy() to fix this warning.
> And then in v5[2], the strscpy() was replaced with strscpy_pad() to
> make sure there's no garbade data and also make get_task_comm() be
> consistent with get_task_comm().
> 
> This commit log didn't clearly describe the historical changes.  So I
> think we can update the commit log and subject with:
> 
> Subject: use strscpy_pad with strlcpy in __set_task_comm
> Commit log:
> strlcpy is not suggested to use by the checkpatch.pl, so we'd better
> recplace it with strscpy.
> To avoid leaving garbage data and be consistent with the usage in
> __get_task_comm(), the strscpy_pad is used here.
> 
> WDYT?

Yes, that makes it clearer what this patch actually does :)

With the subject+description changed

Reviewed-by: David Hildenbrand <david@...hat.com>

Thanks!

-- 
Thanks,

David / dhildenb