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From: Kees Cook <keescook@chromium.org>
To: Yafang Shao <laoar.shao@gmail.com>
Cc: akpm@linux-foundation.org, pmladek@suse.com,
	peterz@infradead.org, valentin.schneider@arm.com,
	mathieu.desnoyers@efficios.com, qiang.zhang@windriver.com,
	robdclark@chromium.org, viro@zeniv.linux.org.uk,
	christian@brauner.io, dietmar.eggemann@arm.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/5] kernel/sched: improve the BUILD_BUG_ON() in get_task_comm()
Date: Wed, 29 Sep 2021 11:12:22 -0700	[thread overview]
Message-ID: <202109291111.31671B6A6@keescook> (raw)
In-Reply-To: <20210929115036.4851-4-laoar.shao@gmail.com>

On Wed, Sep 29, 2021 at 11:50:34AM +0000, Yafang Shao wrote:
> What we really want to guarantee is that the buf size can't be less than
> TASK_COMM_LEN. While the size be greater than TASK_COMM_LEN is
> acceptable.

This makes sense when task_struct::comm is a pointer. (But I think it's
not a good idea to do that.)

-Kees

> 
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> ---
>  include/linux/sched.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index b387b5943db4..959eaef248fc 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1931,7 +1931,7 @@ static inline void set_task_comm(struct task_struct *tsk, const char *from)
>  
>  extern char *__get_task_comm(char *to, size_t len, struct task_struct *tsk);
>  #define get_task_comm(buf, tsk) ({			\
> -	BUILD_BUG_ON(sizeof(buf) != TASK_COMM_LEN);	\
> +	BUILD_BUG_ON(sizeof(buf) < TASK_COMM_LEN);	\
>  	__get_task_comm(buf, sizeof(buf), tsk);		\
>  })
>  
> -- 
> 2.17.1
> 

-- 
Kees Cook

  reply	other threads:[~2021-09-29 18:12 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-29 11:50 [PATCH 0/5] kthread: increase the size of kthread's comm Yafang Shao
2021-09-29 11:50 ` [PATCH 1/5] kernel: replace sizeof(task->comm) with TASK_COMM_LEN Yafang Shao
2021-09-29 18:09   ` Kees Cook
2021-09-30 12:27     ` Yafang Shao
2021-10-03  3:31   ` Al Viro
2021-10-03 14:14     ` Yafang Shao
2021-09-29 11:50 ` [PATCH 2/5] kernel/fork: allocate task->comm dynamicly Yafang Shao
2021-09-29 13:08   ` Yafang Shao
2021-09-29 18:11   ` Kees Cook
2021-09-30 12:41     ` Yafang Shao
2021-09-30 14:51       ` Petr Mladek
2021-10-01 11:58         ` Yafang Shao
2021-09-29 11:50 ` [PATCH 3/5] kernel/sched: improve the BUILD_BUG_ON() in get_task_comm() Yafang Shao
2021-09-29 18:12   ` Kees Cook [this message]
2021-09-30 12:43     ` Yafang Shao
2021-09-29 11:50 ` [PATCH 4/5] kernel: increase the size of kthread's comm Yafang Shao
2021-09-29 18:19   ` Kees Cook
2021-09-30 12:53     ` Yafang Shao
2021-09-29 11:50 ` [PATCH 5/5] kernel/kthread: show a warning if kthread's comm is still trucated Yafang Shao
2021-09-29 18:20   ` Kees Cook
2021-09-30 12:54     ` Yafang Shao
2021-09-30 15:17   ` Petr Mladek
2021-10-01 11:59     ` Yafang Shao
2021-10-03  3:41 ` [PATCH 0/5] kthread: increase the size of kthread's comm Al Viro
2021-10-03 14:20   ` Yafang Shao

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