linux-kernel - Re: [PATCH v14] exec: Fix dead-lock in de_thread with ptrace

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Date: Mon, 22 Jan 2024 14:44:46 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Bernd Edlinger <bernd.edlinger@...mail.de>
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Kees Cook <keescook@...omium.org>,
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	James Morris <jamorris@...ux.microsoft.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Yafang Shao <laoar.shao@...il.com>, Helge Deller <deller@....de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
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	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Hans Liljestrand <ishkamiel@...il.com>
Subject: Re: [PATCH v14] exec: Fix dead-lock in de_thread with ptrace_attach

I'll try to read your email later, just one note for now...

On 01/22, Bernd Edlinger wrote:
>
> > I didn't say that t is a group leader. I said it can be a zombie sub-thread
> > with ->exit_state != 0.
>
> the condition here is
>
> (t != tsk->group_leader || !t->exit_state)
>
> so in other words, if t is a sub-thread, i.e. t != tsk->group_leader
> then the t->exit_state does not count,

Ah indeed, somehow I misread this check as if you skip the sub-threads
with ->exit_state != 0.

Sorry for noise.

Oleg.