linux-kernel - Re: [RFC] [Patch 1/1] [Self Ptrace] System call notification with self

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Message-ID: <20080825165403.GA604@tv-sign.ru>
Date:	Mon, 25 Aug 2008 20:54:03 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Pierre Morel <pmorel@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Roland McGrath <roland@...hat.com>,
	Heiko Carstens <heicars2@...ux.vnet.ibm.com>,
	sameske@...ux.vnet.ibm.com,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [RFC] [Patch 1/1] [Self Ptrace] System call notification with self_ptrace

On 08/25, Pierre Morel wrote:
>
> @@ -550,6 +550,23 @@ asmlinkage long sys_ptrace(long request,
>  		goto out;
>  	}
>
> +	if (request == PTRACE_SELF_ON) {
> +		task_lock(current);
> +		set_thread_flag(TIF_SYSCALL_TRACE);
> +		current->ptrace |= PT_SELF;

I didn't read the whole patch, but this sets PT_SELF without PT_PTRACED
(and without ptrace_attach).

We have some "->ptrace != 0" checks which can misunderstand this. Just
for example, suppose that the task does sys_ptrace(PTRACE_SELF_ON) and
then its parent dies. I guess in that case forget_original_parent()
will hit BUG_ON(p->ptrace), no?

Oleg.

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