iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

KVM: MMU: Fix infinite loop when there is no available mmu page

Browse Source 
commit ed52870f4676489124d8697fd00e6ae6c504e586 upstream.

The below test case can cause infinite loop in kvm when ept=0.

    #include <unistd.h>
    #include <sys/syscall.h>
    #include <string.h>
    #include <stdint.h>
    #include <linux/kvm.h>
    #include <fcntl.h>
    #include <sys/ioctl.h>

    long r[5];
    int main()
    {
    	r[2] = open("/dev/kvm", O_RDONLY);
    	r[3] = ioctl(r[2], KVM_CREATE_VM, 0);
    	r[4] = ioctl(r[3], KVM_CREATE_VCPU, 7);
    	ioctl(r[4], KVM_RUN, 0);
    }

It doesn't setup the memory regions, mmu_alloc_shadow/direct_roots() in
kvm return 1 when kvm fails to allocate root page table which can result
in beblow infinite loop:

    vcpu_run() {
    	for (;;) {
	    	r = vcpu_enter_guest()::kvm_mmu_reload() returns 1
	    	if (r <= 0)
	    		break;
	    	if (need_resched())
	    		cond_resched();
      }
    }

This patch fixes it by returning -ENOSPC when there is no available kvm mmu
page for root page table.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Fixes: 26eeb53cf0f (KVM: MMU: Bail out immediately if there is no available mmu page)
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Wanpeng Li 2017-12-04 22:21:30 -08:00 committed by Greg Kroah-Hartman
parent 5aa30b450a
commit 41e1386388
1 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
arch/x86/kvm/mmu.c
View File

@ -3382,7 +3382,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
spin_lock(&vcpu->kvm->mmu_lock);
if(make_mmu_pages_available(vcpu) < 0) {
spin_unlock(&vcpu->kvm->mmu_lock);
return 1;
return -ENOSPC;
}
sp = kvm_mmu_get_page(vcpu, 0, 0,
vcpu->arch.mmu.shadow_root_level, 1, ACC_ALL);
@ -3397,7 +3397,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
spin_lock(&vcpu->kvm->mmu_lock);
if (make_mmu_pages_available(vcpu) < 0) {
spin_unlock(&vcpu->kvm->mmu_lock);
return 1;
return -ENOSPC;
}
sp = kvm_mmu_get_page(vcpu, i << (30 - PAGE_SHIFT),
i << 30, PT32_ROOT_LEVEL, 1, ACC_ALL);
@ -3437,7 +3437,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
spin_lock(&vcpu->kvm->mmu_lock);
if (make_mmu_pages_available(vcpu) < 0) {
spin_unlock(&vcpu->kvm->mmu_lock);
return 1;
return -ENOSPC;
}
sp = kvm_mmu_get_page(vcpu, root_gfn, 0,
vcpu->arch.mmu.shadow_root_level, 0, ACC_ALL);
@ -3474,7 +3474,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
spin_lock(&vcpu->kvm->mmu_lock);
if (make_mmu_pages_available(vcpu) < 0) {
spin_unlock(&vcpu->kvm->mmu_lock);
return 1;
return -ENOSPC;
}
sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30, PT32_ROOT_LEVEL,
0, ACC_ALL);