Patch "KVM: X86: Fix SMRAM accessing even if VM is shutdown" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

KVM: X86: Fix SMRAM accessing even if VM is shutdown

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-x86-fix-smram-accessing-even-if-vm-is-shutdown.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Wanpeng Li <[email protected]>
Date: Thu, 8 Feb 2018 15:32:45 +0800
Subject: KVM: X86: Fix SMRAM accessing even if VM is shutdown
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From: Wanpeng Li <[email protected]>

commit 95e057e25892eaa48cad1e2d637b80d0f1a4fac5 upstream.

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.

---
 arch/x86/kvm/mmu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -2698,7 +2698,7 @@ static int kvm_handle_bad_page(struct kv
 		return 0;
 	}
 
-	return -EFAULT;
+	return RET_PF_EMULATE;
 }
 
 static void transparent_hugepage_adjust(struct kvm_vcpu *vcpu,

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/kvm-x86-fix-smram-accessing-even-if-vm-is-shutdown.patch