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 3052a59a3065..1f6b0d9b0c85 100644 --- a/arch/x86/kvm/page_track.c +++ b/arch/x86/kvm/page_track.c @@ -169,13 +169,13 @@ 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 417abc9ba1ad..70cb18f89029 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9039,9 +9039,15 @@ 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);

@@ -9068,7 +9074,6 @@ 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);

if (kvm_x86_ops->vm_init)

Acked-by: Paolo Bonzini pbonzini@redhat.com