linux-kernel - Re: [PATCH v2] execve: must clear current->clear_child

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Message-ID: <4A73F44E.1010508@gmail.com>
Date:	Sat, 01 Aug 2009 09:52:46 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, drepper@...hat.com, jens@...one.net,
	mingo@...e.hu, peterz@...radead.org, sonnyrao@...ibm.com,
	stable@...nel.org, tglx@...utronix.de
Subject: Re: [PATCH v2] execve: must clear current->clear_child_tid

Oleg Nesterov a écrit :
> On 08/01, Eric Dumazet wrote:
>> I only wonder about core dumping, since mm_release() is also used by exiting tasks.
>>
>> Isnt clear_child_tid used by gdb or other debugger ?
> 
> Afaics it is not...
> 
> At least, I can't see how gdb (or any other user-space app) can figure
> out the value of ->clear_child_tid.
> 

Yep, this was from old Unixes time, when core file included the 'u' structure ...

Dont worry ;)


> 
> 
> Not that this really matters, but please note also that it is possible
> that the coredumping task has ->clear_child_tid == NULL anyway, even
> without this change. The PF_SIGNALED check in mm_release() is not 100&
> reliable.
> 
> Suppose a thread T sleeps in do_exit()->ptrace_event(PT_TRACE_EXIT) path.
> Another thread starts a coredump and kills T via zap_process(). This wakes
> up T, it calls exit_mm()->mm_release() without PF_SIGNALED.
> 
> Oleg.
> 

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