From: Jarkko Sakkinen <jarkko@kernel.org>
To: x86@kernel.org
Cc: linux-kernel@vger.kernel.org, linux-sgx@vger.kernel.org,
Jarkko Sakkinen <jarkko@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>,
"H. Peter Anvin" <hpa@zytor.com>,
Jethro Beekman <jethro@fortanix.com>
Subject: [PATCH v3] x86/sgx: Synchronize encl->srcu in sgx_encl_release().
Date: Wed, 16 Dec 2020 15:49:20 +0200 [thread overview]
Message-ID: <20201216134920.21161-1-jarkko@kernel.org> (raw)
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().
Fixes: 1728ab54b4be ("x86/sgx: Add a page reclaimer")
Suggested-by: Sean Christopherson <seanjc@google.com>
Suggested-by: Haitao Huang <haitao.huang@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v3: Fine-tuned tags, and added missing change log for v2.
v2: Switch to synchronize_srcu_expedited().
arch/x86/kernel/cpu/sgx/encl.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index ee50a5010277..fe7256db6e73 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -438,6 +438,12 @@ void sgx_encl_release(struct kref *ref)
if (encl->backing)
fput(encl->backing);
+ /*
+ * Each sgx_mmu_notifier_release() starts a grace period. Therefore, an
+ * additional sync is required here.
+ */
+ synchronize_srcu_expedited(&encl->srcu);
+
cleanup_srcu_struct(&encl->srcu);
WARN_ON_ONCE(!list_empty(&encl->mm_list));
--
2.27.0
next reply other threads:[~2020-12-16 13:50 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-16 13:49 Jarkko Sakkinen [this message]
2021-01-04 20:22 ` [PATCH v3] x86/sgx: Synchronize encl->srcu in sgx_encl_release() Haitao Huang
2021-01-11 23:41 ` Jarkko Sakkinen
2021-01-05 14:57 ` Borislav Petkov
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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