linux-kernel - [PATCH 5.1 017/405] KVM: nVMX: Fix using __this_cpu

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Message-Id: <20190530030541.409293451@linuxfoundation.org>
Date:   Wed, 29 May 2019 20:00:15 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: [PATCH 5.1 017/405] KVM: nVMX: Fix using __this_cpu_read() in preemptible context

From: Wanpeng Li <wanpengli@...cent.com>

commit 541e886f7972cc647804dbb4909189e67987a945 upstream.

 BUG: using __this_cpu_read() in preemptible [00000000] code: qemu-system-x86/4590
  caller is nested_vmx_enter_non_root_mode+0xebd/0x1790 [kvm_intel]
  CPU: 4 PID: 4590 Comm: qemu-system-x86 Tainted: G           OE     5.1.0-rc4+ #1
  Call Trace:
   dump_stack+0x67/0x95
   __this_cpu_preempt_check+0xd2/0xe0
   nested_vmx_enter_non_root_mode+0xebd/0x1790 [kvm_intel]
   nested_vmx_run+0xda/0x2b0 [kvm_intel]
   handle_vmlaunch+0x13/0x20 [kvm_intel]
   vmx_handle_exit+0xbd/0x660 [kvm_intel]
   kvm_arch_vcpu_ioctl_run+0xa2c/0x1e50 [kvm]
   kvm_vcpu_ioctl+0x3ad/0x6d0 [kvm]
   do_vfs_ioctl+0xa5/0x6e0
   ksys_ioctl+0x6d/0x80
   __x64_sys_ioctl+0x1a/0x20
   do_syscall_64+0x6f/0x6c0
   entry_SYSCALL_64_after_hwframe+0x49/0xbe

Accessing per-cpu variable should disable preemption, this patch extends the
preemption disable region for __this_cpu_read().

Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
Fixes: 52017608da33 ("KVM: nVMX: add option to perform early consistency checks via H/W")
Cc: stable@...r.kernel.org
Reviewed-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kvm/vmx/nested.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2792,14 +2792,13 @@ static int nested_vmx_check_vmentry_hw(s
 	      : "cc", "memory"
 	);
 
-	preempt_enable();
-
 	if (vmx->msr_autoload.host.nr)
 		vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, vmx->msr_autoload.host.nr);
 	if (vmx->msr_autoload.guest.nr)
 		vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, vmx->msr_autoload.guest.nr);
 
 	if (vm_fail) {
+		preempt_enable();
 		WARN_ON_ONCE(vmcs_read32(VM_INSTRUCTION_ERROR) !=
 			     VMXERR_ENTRY_INVALID_CONTROL_FIELD);
 		return 1;
@@ -2811,6 +2810,7 @@ static int nested_vmx_check_vmentry_hw(s
 	local_irq_enable();
 	if (hw_breakpoint_active())
 		set_debugreg(__this_cpu_read(cpu_dr7), 7);
+	preempt_enable();
 
 	/*
 	 * A non-failing VMEntry means we somehow entered guest mode with