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From: Borislav Petkov <bp@alien8.de>
To: Jarkko Sakkinen <jarkko@kernel.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
	linux-sgx@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>, "H. Peter Anvin" <hpa@zytor.com>,
	Jethro Beekman <jethro@fortanix.com>
Subject: Re: [PATCH v3] x86/sgx: Synchronize encl->srcu in sgx_encl_release().
Date: Tue, 5 Jan 2021 15:57:49 +0100	[thread overview]
Message-ID: <20210105145749.GF28649@zn.tnic> (raw)
In-Reply-To: <20201216134920.21161-1-jarkko@kernel.org>

On Wed, Dec 16, 2020 at 03:49:20PM +0200, Jarkko Sakkinen wrote:
> Add synchronize_srcu_expedited() to sgx_encl_release() to catch a grace
> period initiated by sgx_mmu_notifier_release().
> 
> A trivial example of a failing sequence with tasks A and B:
> 
> 1. A: -> sgx_release()
> 2. B: -> sgx_mmu_notifier_release()
> 3. B: -> list_del_rcu()
> 3. A: -> sgx_encl_release()
> 4. A: -> cleanup_srcu_struct()
> 
> The loop in sgx_release() observes an empty list because B has removed its
> entry in the middle, and calls cleanup_srcu_struct() before B has a chance
> to calls synchronize_srcu().

Leading to what? NULL ptr?

https://lkml.kernel.org/r/X9e2jOWz1hfXVpQ5@google.com

already suggested that you should explain the bug better and add the
splat but I'm still missing that explanation.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

  parent reply	other threads:[~2021-01-05 14:58 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-16 13:49 [PATCH v3] x86/sgx: Synchronize encl->srcu in sgx_encl_release() Jarkko Sakkinen
2021-01-04 20:22 ` Haitao Huang
2021-01-11 23:41   ` Jarkko Sakkinen
2021-01-05 14:57 ` Borislav Petkov [this message]
2021-01-12  0:08   ` Jarkko Sakkinen
2021-01-12 18:35     ` Borislav Petkov
2021-01-12 20:11       ` Paul E. McKenney
2021-01-13 17:18       ` Jarkko Sakkinen
2021-01-13 17:46         ` Paul E. McKenney
2021-01-13 18:00           ` Borislav Petkov
2021-01-13 18:22             ` Paul E. McKenney
2021-01-15  1:49           ` Jarkko Sakkinen
2021-01-14  4:42     ` Haitao Huang
2021-01-15  9:58       ` Jarkko Sakkinen

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