From 95e057e25892eaa48cad1e2d637b80d0f1a4fac5 Mon Sep 17 00:00:00 2001
From: Wanpeng Li <wanpengli@tencent.com>
Date: Thu, 8 Feb 2018 15:32:45 +0800
Subject: [PATCH] KVM: X86: Fix SMRAM accessing even if VM is shutdown
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Reported by syzkaller:
WARNING: CPU: 6 PID: 2434 at arch/x86/kvm/vmx.c:6660 handle_ept_misconfig+0x54/0x1e0 [kvm_intel]
CPU: 6 PID: 2434 Comm: repro_test Not tainted 4.15.0+ #4
RIP: 0010:handle_ept_misconfig+0x54/0x1e0 [kvm_intel]
Call Trace:
vmx_handle_exit+0xbd/0xe20 [kvm_intel]
kvm_arch_vcpu_ioctl_run+0xdaf/0x1d50 [kvm]
kvm_vcpu_ioctl+0x3e9/0x720 [kvm]
do_vfs_ioctl+0xa4/0x6a0
SyS_ioctl+0x79/0x90
entry_SYSCALL_64_fastpath+0x25/0x9c
The testcase creates a first thread to issue KVM_SMI ioctl, and then creates
a second thread to mmap and operate on the same vCPU. This triggers a race
condition when running the testcase with multiple threads. Sometimes one thread
exits with a triple fault while another thread mmaps and operates on the same
vCPU. Because CS=0x3000/IP=0x8000 is not mapped, accessing the SMI handler
results in an EPT misconfig. This patch fixes it by returning RET_PF_EMULATE
in kvm_handle_bad_page(), which will go on to cause an emulation failure and an
exit with KVM_EXIT_INTERNAL_ERROR.
Reported-by: syzbot+c1d9517cab094dae65e446c0c5b4de6c40f4dc58@syzkaller.appspotmail.com
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim KrÄmář <rkrcmar@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/mmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 8eca1d04aeb8..6c5a82c74750 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3029,7 +3029,7 @@ static int kvm_handle_bad_page(struct kvm_vcpu *vcpu, gfn_t gfn, kvm_pfn_t pfn)
return RET_PF_RETRY;
}
- return -EFAULT;
+ return RET_PF_EMULATE;
}
static void transparent_hugepage_adjust(struct kvm_vcpu *vcpu,
--
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