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From: Roland McGrath <roland@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Andi Kleen <andi@firstfloor.org>,
	David Howells <dhowells@redhat.com>,
	Neil Horman <nhorman@tuxdriver.com>,
	Rusty Russell <rusty@rustcorp.com.au>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] wait_for_helper: SIGCHLD from user-space can lead to use-after-free
Date: Wed, 10 Mar 2010 12:32:09 -0800 (PST)	[thread overview]
Message-ID: <20100310203209.54168BCCD@magilla.sf.frob.com> (raw)
In-Reply-To: Oleg Nesterov's message of  Wednesday, 10 March 2010 18:16:34 +0100 <20100310171634.GA1039@redhat.com>

SIGCHLD being blocked doesn't affect reaping, so SIG_IGN or sa_flags &
SA_NOCLDWAIT is the only thing that would do this.  How does that come
about here in this kthread?  Is it inherited from the instigating user
process?  If so, then SA_NOCLDWAIT is as much a problem as SIG_IGN.  
Or I guess maybe it's from ignore_signals() in kthreadd()?
In that case SIG_IGN is indeed all that matters.  (I don't really
know all the kthread/kmod/userhelper code organization.)

Perhaps it would be cleaner to do:

	flush_signal_handlers(current, 1);

in wait_for_helper.  That should make it redundant in ____call_usermodehelper,
so it could be removed from there.


Thanks,
Roland

  parent reply	other threads:[~2010-03-10 20:32 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-03-10 17:16 [PATCH] wait_for_helper: SIGCHLD from user-space can lead to use-after-free Oleg Nesterov
2010-03-10 18:07 ` Neil Horman
2010-03-10 20:32 ` Roland McGrath [this message]
2010-03-10 21:19   ` Oleg Nesterov
2010-03-10 21:27     ` Roland McGrath

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