linux-kernel - Re: [PATCH RFC 0/2] Dynamically allocate memory to store task's full name

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Message-ID: <202503141420.37D605B2@keescook>
Date: Fri, 14 Mar 2025 14:25:09 -0700
From: Kees Cook <kees@...nel.org>
To: Bhupesh <bhupesh@...lia.com>
Cc: akpm@...ux-foundation.org, kernel-dev@...lia.com,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
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Subject: Re: [PATCH RFC 0/2] Dynamically allocate memory to store task's full
 name

On Fri, Mar 14, 2025 at 10:57:13AM +0530, Bhupesh wrote:
> While working with user-space debugging tools which work especially
> on linux gaming platforms, I found that the task name is truncated due
> to the limitation of TASK_COMM_LEN.
> 
> For example, currently running 'ps', the task->comm value of a long
> task name is truncated due to the limitation of TASK_COMM_LEN.
>     create_very_lon
> 
> This leads to the names passed from userland via pthread_setname_np()
> being truncated.

So there have been long discussions about "comm", and it mainly boils
down to "leave it alone". For the /proc-scraping tools like "ps" and
"top", they check both "comm" and "cmdline", depending on mode. The more
useful (and already untruncated) stuff is in "cmdline", so I suspect it
may make more sense to have pthread_setname_np() interact with that
instead. Also TASK_COMM_LEN is basically considered userspace ABI at
this point and we can't sanely change its length without breaking the
world.

Best to use /proc/$pid/task/$tid/cmdline IMO...

-Kees

> will be shown in 'ps'. For example:
>     create_very_long_name_user_space_script.sh
> 
> Bhupesh (2):
>   exec: Dynamically allocate memory to store task's full name
>   fs/proc: Pass 'task->full_name' via 'proc_task_name()'
> 
>  fs/exec.c             | 21 ++++++++++++++++++---
>  fs/proc/array.c       |  2 +-
>  include/linux/sched.h |  9 +++++++++
>  3 files changed, 28 insertions(+), 4 deletions(-)
> 
> -- 
> 2.38.1
> 

-- 
Kees Cook