linux-kernel - Re: yama_ptrace_access_check(): possible recursive locking detected

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Date:	Mon, 30 Jul 2012 10:00:00 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Fengguang Wu <fengguang.wu@...el.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: yama_ptrace_access_check(): possible recursive locking detected

On Thu, Jul 26, 2012 at 8:41 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> On 07/26, Fengguang Wu wrote:
>>
>> Here is a recursive lock possibility:
>>
>>         ptrace_may_access()
>> =>        task_lock(task);
>>             yama_ptrace_access_check()
>>               get_task_comm()
>> =>              task_lock(task);
>
> I think yama_ptrace_access_check() can simply use ->comm
>
> Oleg.
>
> --- x/security/yama/yama_lsm.c
> +++ x/security/yama/yama_lsm.c
> @@ -279,12 +279,9 @@ static int yama_ptrace_access_check(stru
>         }
>
>         if (rc) {
> -               char name[sizeof(current->comm)];
>                 printk_ratelimited(KERN_NOTICE
>                         "ptrace of pid %d was attempted by: %s (pid %d)\n",
> -                       child->pid,
> -                       get_task_comm(name, current),
> -                       current->pid);
> +                       child->pid, current->comm, current->pid);
>         }
>
>         return rc;
>

Great catch, thanks! I've sent Oleg's suggestion (with an added
comment) separately.

-Kees

-- 
Kees Cook
Chrome OS Security
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