[PATCH 5.14 169/172] KVM: x86: Handle SRCU initialization failure during page track init

Greg Kroah-Hartman
2021-10-04T13:43:32Z

From: Haimin Zhang <tcs_kernel@tencent.com>

commit eb7511bf9182292ef1df1082d23039e856d1ddfb upstream.

Check the return of init_srcu_struct(), which can fail due to OOM, when
initializing the page track mechanism. Lack of checking leads to a NULL
pointer deref found by a modified syzkaller.

Reported-by: TCS Robot <tcs_robot@tencent.com>
Signed-off-by: Haimin Zhang <tcs_kernel@tencent.com>
Message-Id: <1630636626-12262-1-git-send-email-tcs_kernel@tencent.com>
[Move the call towards the beginning of kvm_arch_init_vm. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/include/asm/kvm_page_track.h | 2 +-
arch/x86/kvm/mmu/page_track.c | 4 ++--
arch/x86/kvm/x86.c | 7 ++++++-
3 files changed, 9 insertions(+), 4 deletions(-)

--- a/arch/x86/include/asm/kvm_page_track.h
+++ b/arch/x86/include/asm/kvm_page_track.h
@@ -46,7 +46,7 @@ struct kvm_page_track_notifier_node {
struct kvm_page_track_notifier_node *node);
};

-void kvm_page_track_init(struct kvm *kvm);
+int kvm_page_track_init(struct kvm *kvm);
void kvm_page_track_cleanup(struct kvm *kvm);

void kvm_page_track_free_memslot(struct kvm_memory_slot *slot);
--- a/arch/x86/kvm/mmu/page_track.c
+++ b/arch/x86/kvm/mmu/page_track.c
@@ -163,13 +163,13 @@ void kvm_page_track_cleanup(struct kvm *
cleanup_srcu_struct(&head->track_srcu);
}

-void kvm_page_track_init(struct kvm *kvm)
+int kvm_page_track_init(struct kvm *kvm)
{
struct kvm_page_track_notifier_head *head;

head = &kvm->arch.track_notifier_head;
- init_srcu_struct(&head->track_srcu);
INIT_HLIST_HEAD(&head->track_notifier_list);
+ return init_srcu_struct(&head->track_srcu);
}

/*
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11093,9 +11093,15 @@ void kvm_arch_free_vm(struct kvm *kvm)

int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
{
+ int ret;
+
if (type)
return -EINVAL;

+ ret = kvm_page_track_init(kvm);
+ if (ret)
+ return ret;
+
INIT_HLIST_HEAD(&kvm->arch.mask_notifier_list);
INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
INIT_LIST_HEAD(&kvm->arch.zapped_obsolete_pages);
@@ -11128,7 +11134,6 @@ int kvm_arch_init_vm(struct kvm *kvm, un

kvm_apicv_init(kvm);
kvm_hv_init_vm(kvm);
- kvm_page_track_init(kvm);
kvm_mmu_init_vm(kvm);

return static_call(kvm_x86_vm_init)(kvm);