linux-kernel - Re: [PATCH v2] cgroup: align the comm length with TASK_COMM

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Message-ID: <20220925224204.4e5d341e@gandalf.local.home>
Date:   Sun, 25 Sep 2022 22:42:04 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Kassey Li <quic_yingangl@...cinc.com>
Cc:     <mingo@...hat.com>, <tj@...nel.org>,
        <william.kucharski@...cle.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] cgroup: align the comm length with TASK_COMM_LEN

On Mon, 26 Sep 2022 10:18:55 +0800
Kassey Li <quic_yingangl@...cinc.com> wrote:

> >> @@ -139,12 +139,12 @@ DECLARE_EVENT_CLASS(cgroup_migrate,
> >>   		__entry->dst_level = dst_cgrp->level;
> >>   		__assign_str(dst_path, path);
> >>   		__entry->pid = task->pid;
> >> -		__assign_str(comm, task->comm);
> >> +		memcpy(__entry->comm, task->comm, TASK_COMM_LEN);  
> 	I think the problem is here, __assign_str using strcpy
> 	the task->comm here tail is not '\0'
> 	that's why it out of bounds access.
> 

If this is the case, then there's a lot more than just tracing that will
break. There are other places in the kernel has used strcpy() on task->comm,
and many more that do "%s" on task->comm, which would also crash on this.

> 	do you want to this version or just modify the memcpy or strncpy to do 
> with a known length ?  please give suggest so I can modify .

I'm guessing a problem exists elsewhere that makes it look like this is the
issue. I suggest finding where the '\0' is dropped (if that is indeed the
case).

-- Steve