KVM: x86: Handle SRCU initialization failure during page track init

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>

diff --git a/arch/x86/include/asm/kvm_page_track.h b/arch/x86/include/asm/kvm_page_track.h
index 87bd602..6a5f3ac 100644 (file)
--- 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);

diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
index 269f11f..21427e8 100644 (file)
--- a/arch/x86/kvm/mmu/page_track.c
+++ b/arch/x86/kvm/mmu/page_track.c
@@ -164,13 +164,13 @@ void kvm_page_track_cleanup(struct kvm *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);
 }
 
 /*

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8a83dd1..42c5c7a 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11144,9 +11144,15 @@ 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);
@@ -11179,7 +11185,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 
        kvm_apicv_init(kvm);
        kvm_hv_init_vm(kvm);
-       kvm_page_track_init(kvm);
        kvm_mmu_init_vm(kvm);
        kvm_xen_init_vm(kvm);