linux-kernel - Re: [patch 1/6] mmu

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Message-ID: <20080129160737.GV3058@sgi.com>
Date:	Tue, 29 Jan 2008 10:07:37 -0600
From:	Robin Holt <holt@....com>
To:	Christoph Lameter <clameter@....com>
Cc:	Andrea Arcangeli <andrea@...ranet.com>, Robin Holt <holt@....com>,
	Avi Kivity <avi@...ranet.com>, Izik Eidus <izike@...ranet.com>,
	Nick Piggin <npiggin@...e.de>, kvm-devel@...ts.sourceforge.net,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, steiner@....com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com, Hugh Dickins <hugh@...itas.com>
Subject: Re: [patch 1/6] mmu_notifier: Core code

I am going to seperate my comments into individual replies to help
reduce the chance they are lost.

> +void mmu_notifier_release(struct mm_struct *mm)
...
> +		hlist_for_each_entry_safe_rcu(mn, n, t,
> +					  &mm->mmu_notifier.head, hlist) {
> +			if (mn->ops->release)
> +				mn->ops->release(mn, mm);
> +			hlist_del(&mn->hlist);

This is a use-after-free issue.  The hlist_del_rcu needs to be done before
the callout as the structure containing the mmu_notifier structure will
need to be freed from within the ->release callout.

Thanks,
Robin
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