linux-kernel - Re: [PATCH] tracepoint: don't make assumptions about length of string on task rename

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Message-ID: <20150828110251.41b6b805@gandalf.local.home>
Date:	Fri, 28 Aug 2015 11:02:51 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracepoint: don't make assumptions about length of
 string on task rename

On Fri, 28 Aug 2015 07:06:58 -0400
Sasha Levin <sasha.levin@...cle.com> wrote:

> While the dest comm string size is assured to be at least TASK_COMM_LEN long,
> doing a memcpy() also adds the assumption that the source is at least that
> long as well, which isn't assured, and isn't true in cases such as:
> 
> 	set_task_comm(worker->task, "kworker/dying");
> 
> This leads to accessing invalid memory.
> 
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>

Acked-by: Steven Rostedt <rostedt@...dmis.org>

Should this go to stable as well?

Also, as the memcpy was just faster than a strcpy, the static length
was used. Perhaps we should convert that to a dynamic length string.
But that should be a separate patch as this one fixes a possible bug,
and the conversion to a dynamic string is just an enhancement.

-- Steve


> ---
>  include/trace/events/task.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/trace/events/task.h b/include/trace/events/task.h
> index dee3bb1..2cca6cd 100644
> --- a/include/trace/events/task.h
> +++ b/include/trace/events/task.h
> @@ -46,7 +46,7 @@ TRACE_EVENT(task_rename,
>  	TP_fast_assign(
>  		__entry->pid = task->pid;
>  		memcpy(entry->oldcomm, task->comm, TASK_COMM_LEN);
> -		memcpy(entry->newcomm, comm, TASK_COMM_LEN);
> +		strlcpy(entry->newcomm, comm, TASK_COMM_LEN);
>  		__entry->oom_score_adj = task->signal->oom_score_adj;
>  	),
>  

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