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%3Ba=su...

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@vger.kernel.org know about it.

From ed52870f4676489124d8697fd00e6ae6c504e586 Mon Sep 17 00:00:00 2001

From: Wanpeng Li wanpeng.li@hotmail.com Date: Mon, 4 Dec 2017 22:21:30 -0800 Subject: KVM: MMU: Fix infinite loop when there is no available mmu page MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

From: Wanpeng Li wanpeng.li@hotmail.com

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

--- 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@hotmail.com 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