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From: Jarkko Sakkinen <jarkko@kernel.org>
To: Dave Hansen <dave.hansen@intel.com>
Cc: linux-sgx@vger.kernel.org, stable@vger.kernel.org,
	Sean Christopherson <seanjc@google.com>,
	Haitao Huang <haitao.huang@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Jethro Beekman <jethro@fortanix.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] x86/sgx: Fix use-after-free in sgx_mmu_notifier_release()
Date: Wed, 3 Feb 2021 23:54:42 +0200	[thread overview]
Message-ID: <YBsbojMEeq3pCNhy@kernel.org> (raw)
In-Reply-To: <8df884af-825e-bae0-f0c3-c3e97f48d138@intel.com>

On Wed, Feb 03, 2021 at 07:46:48AM -0800, Dave Hansen wrote:
> On 1/30/21 11:20 AM, Jarkko Sakkinen wrote:
> ...
> > Example scenario would such that all removals "side-channel" through
> > the notifier callback. Then mmu_notifier_unregister() gets called
> > exactly zero times. No MMU notifier srcu sync would be then happening.
> > 
> > NOTE: There's bunch of other examples, I'm just giving one.
> 
> Could you flesh this out a bit?  I don't quite understand the scenario
> from what you describe above.
> 
> In any case, I'm open to other implementations that fix the race we know
> about.  If you think you have a better fix, I'm happy to review it and
> make sure it closes the other race.

I'll bake up a new patch. Generally speaking, I think why this has been so
difficult, is because of a chicken-egg-problem. The whole issue should be
sorted when a new entry is first added to the mm_list, i.e. increase the
refcount for each added entry.

/Jarkko

      reply	other threads:[~2021-02-03 21:55 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-28 12:58 [PATCH v5] x86/sgx: Fix use-after-free in sgx_mmu_notifier_release() Jarkko Sakkinen
2021-01-28 16:33 ` Dave Hansen
2021-01-30 19:20   ` Jarkko Sakkinen
2021-01-30 19:26     ` Jarkko Sakkinen
2021-02-03 15:46     ` Dave Hansen
2021-02-03 21:54       ` Jarkko Sakkinen [this message]

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