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

Sasha Levin
2021-10-06T11:13:39Z

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);
--
2.33.0