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Date:   Mon, 25 Oct 2021 14:06:54 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        Yafang Shao <laoar.shao@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
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        Petr Mladek <pmladek@suse.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Valentin Schneider <valentin.schneider@arm.com>,
        "Zhang, Qiang" <qiang.zhang@windriver.com>, robdclark@chromium.org,
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        Dietmar Eggemann <dietmar.eggemann@arm.com>,
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        "David S. Miller" <davem@davemloft.net>,
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Subject: Re: [PATCH v6 00/12] extend task comm from 16 to 24
Message-ID: <202110251406.56F87A3522@keescook>
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On Mon, Oct 25, 2021 at 05:05:03PM -0400, Steven Rostedt wrote:
> On Mon, 25 Oct 2021 11:10:09 -0700
> Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
> 
> > It looks like a churn that doesn't really address the problem.
> > If we were to allow long names then make it into a pointer and use 16 byte
> > as an optimized storage for short names. Any longer name would be a pointer.
> > In other words make it similar to dentry->d_iname.
> 
> That would be quite a bigger undertaking too, as it is assumed throughout
> the kernel that the task->comm is TASK_COMM_LEN and is nul terminated. And
> most locations that save the comm simply use a fixed size string of
> TASK_COMM_LEN. Not saying its not feasible, but it would require a lot more
> analysis of the impact by changing such a fundamental part of task struct
> from a static to something requiring allocation.
> 
> Unless you are suggesting that we truncate like normal the 16 byte names
> (to a max of 15 characters), and add a way to hold the entire name for
> those locations that understand it.

Agreed -- this is a small change for what is already an "uncommon"
corner case. I don't think this needs to suddenly become an unbounded
string. :)

-- 
Kees Cook