Re: [PATCH MANUALSEL 5.4 1/4] KVM: x86: Handle SRCU initialization failure during page track init

Paolo Bonzini
2021-10-06T11:23:48Z

On 06/10/21 13:12, Sasha Levin wrote:
> From: Haimin Zhang <tcs_kernel@tencent.com>
>
> [ Upstream commit eb7511bf9182292ef1df1082d23039e856d1ddfb ]
>
> 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: Sasha Levin <sashal@kernel.org>
> ---
> arch/x86/include/asm/kvm_page_track.h | 2 +-
> arch/x86/kvm/page_track.c | 4 ++--
> arch/x86/kvm/x86.c | 7 ++++++-
> 3 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_page_track.h b/arch/x86/include/asm/kvm_page_track.h
> index 172f9749dbb2..5986bd4aacd6 100644
> --- 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 *free,
> diff --git a/arch/x86/kvm/page_track.c b/arch/x86/kvm/page_track.c
> index 3521e2d176f2..ef89a3ede425 100644
> --- a/arch/x86/kvm/page_track.c
> +++ b/arch/x86/kvm/page_track.c
> @@ -167,13 +167,13 @@ 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 f1a0eebdcf64..69e286edb2c9 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9585,9 +9585,15 @@ void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu)
>
> 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);
> @@ -9614,7 +9620,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> INIT_DELAYED_WORK(&kvm->arch.kvmclock_sync_work, kvmclock_sync_fn);
>
> kvm_hv_init_vm(kvm);
> - kvm_page_track_init(kvm);
> kvm_mmu_init_vm(kvm);
>
> return kvm_x86_ops->vm_init(kvm);
>

Acked-by: Paolo Bonzini <pbonzini@redhat.com>