linux-kernel - [PATCH] kvm: async_pf: fix rcu_irq

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Message-Id: <20170426145626.6407-1-pbonzini@redhat.com>
Date:   Wed, 26 Apr 2017 16:56:26 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     rkrcmar@...hat.com, ross.zwisler@...ux.intel.com,
        paulmck@...ux.vnet.ibm.com, jack@...e.cz,
        linux-ext4@...r.kernel.org, tytso@....edu, josh@...htriplett.org,
        stable@...r.kernel.org
Subject: [PATCH] kvm: async_pf: fix rcu_irq_enter() with irqs enabled

native_safe_halt enables interrupts, and you just shouldn't
call rcu_irq_enter() with interrupts enabled.  Reorder the
call with the following local_irq_disable() to respect the
invariant.

Reported-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc: stable@...r.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kernel/kvm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 14f65a5f938e..2a7835932b71 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -161,8 +161,8 @@ void kvm_async_pf_task_wait(u32 token)
 			 */
 			rcu_irq_exit();
 			native_safe_halt();
-			rcu_irq_enter();
 			local_irq_disable();
+			rcu_irq_enter();
 		}
 	}
 	if (!n.halted)
-- 
2.9.3