This is a note to let you know that I've just added the patch titled
KVM: MMU: Fix infinite loop when there is no available mmu page
to the 4.14-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-mmu-fix-infinite-loop-when-there-is-no-available-mmu-page.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ed52870f4676489124d8697fd00e6ae6c504e586 Mon Sep 17 00:00:00 2001
From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
Date: Mon, 4 Dec 2017 22:21:30 -0800
Subject: KVM: MMU: Fix infinite loop when there is no available mmu page
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From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Fixes: 26eeb53cf0f (KVM: MMU: Bail out immediately if there is no available mmu page)
Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/mmu.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3382,7 +3382,7 @@ static int mmu_alloc_direct_roots(struct
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
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
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
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);
Patches currently in stable-queue which might be from wanpeng.li@xxxxxxxxxxx are
queue-4.14/kvm-mmu-fix-infinite-loop-when-there-is-no-available-mmu-page.patch
queue-4.14/kvm-x86-fix-load-rflags-w-o-the-fixed-bit.patch