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

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Message-Id: <20211006111250.264294-1-sashal@kernel.org>
Date:   Wed,  6 Oct 2021 07:12:47 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Haimin Zhang <tcs_kernel@...cent.com>,
        TCS Robot <tcs_robot@...cent.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, kvm@...r.kernel.org
Subject: [PATCH MANUALSEL 5.4 1/4] KVM: x86: Handle SRCU initialization failure during page track init

From: Haimin Zhang <tcs_kernel@...cent.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@...cent.com>
Signed-off-by: Haimin Zhang <tcs_kernel@...cent.com>
Message-Id: <1630636626-12262-1-git-send-email-tcs_kernel@...cent.com>
[Move the call towards the beginning of kvm_arch_init_vm. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.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