From: Jarkko Sakkinen <jarkko@kernel.org>
To: linux-sgx@vger.kernel.org
Cc: dave.hansen@intel.com, Jarkko Sakkinen <jarkko@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: [PATCH v5] x86/sgx: Fix use-after-free in sgx_mmu_notifier_release()
Date: Thu, 28 Jan 2021 14:58:23 +0200 [thread overview]
Message-ID: <20210128125823.18660-1-jarkko@kernel.org> (raw)
The most trivial example of a race condition can be demonstrated by this
sequence where mm_list contains just one entry:
CPU A CPU B
-> sgx_release()
-> sgx_mmu_notifier_release()
-> list_del_rcu()
<- list_del_rcu()
-> kref_put()
-> sgx_encl_release()
-> synchronize_srcu()
-> cleanup_srcu_struct()
A sequence similar to this has also been spotted in tests under high
stress:
[ +0.000008] WARNING: CPU: 3 PID: 7620 at kernel/rcu/srcutree.c:374 cleanup_srcu_struct+0xed/0x100
Albeit not spotted in the tests, it's also entirely possible that the
following scenario could happen:
CPU A CPU B
-> sgx_release()
-> sgx_mmu_notifier_release()
-> list_del_rcu()
-> kref_put()
-> sgx_encl_release()
-> cleanup_srcu_struct()
<- cleanup_srcu_struct()
-> synchronize_srcu()
This scenario would lead into use-after free in cleaup_srcu_struct().
Fix this by taking a reference to the enclave in
sgx_mmu_notifier_release().
Cc: stable@vger.kernel.org
Fixes: 1728ab54b4be ("x86/sgx: Add a page reclaimer")
Suggested-by: Sean Christopherson <seanjc@google.com>
Reported-by: Haitao Huang <haitao.huang@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v5:
- To make sure that the instance does not get deleted use kref_get()
kref_put(). This also removes the need for additional
synchronize_srcu().
v4:
- Rewrite the commit message.
- Just change the call order. *_expedited() is out of scope for this
bug fix.
v3: Fine-tuned tags, and added missing change log for v2.
v2: Switch to synchronize_srcu_expedited().
arch/x86/kernel/cpu/sgx/encl.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index ee50a5010277..5ecbcf94ec2a 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -465,6 +465,7 @@ static void sgx_mmu_notifier_release(struct mmu_notifier *mn,
spin_lock(&encl_mm->encl->mm_lock);
list_for_each_entry(tmp, &encl_mm->encl->mm_list, list) {
if (tmp == encl_mm) {
+ kref_get(&encl_mm->encl->refcount);
list_del_rcu(&encl_mm->list);
break;
}
@@ -474,6 +475,7 @@ static void sgx_mmu_notifier_release(struct mmu_notifier *mn,
if (tmp == encl_mm) {
synchronize_srcu(&encl_mm->encl->srcu);
mmu_notifier_put(mn);
+ kref_put(&encl_mm->encl->refcount, sgx_encl_release);
}
}
--
2.30.0
next reply other threads:[~2021-01-28 12:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-28 12:58 Jarkko Sakkinen [this message]
2021-01-28 16:33 ` [PATCH v5] x86/sgx: Fix use-after-free in sgx_mmu_notifier_release() 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
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