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From: Oliver Upton <oupton@google.com>
To: kvmarm@lists.cs.columbia.edu
Cc: kvm@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	Peter Shier <pshier@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	stable@kernel.org, linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/4] KVM: arm64: vgic: Don't assume the VM debugfs directory exists
Date: Sat,  2 Apr 2022 17:40:41 +0000	[thread overview]
Message-ID: <20220402174044.2263418-2-oupton@google.com> (raw)
In-Reply-To: <20220402174044.2263418-1-oupton@google.com>

Unfortunately, there is no guarantee that KVM was able to instantiate a
debugfs directory for a particular VM. To that end, KVM shouldn't even
attempt to create new debugfs files in this case. If the specified
parent dentry is NULL, debugfs_create_file() will instantiate files at
the root of debugfs.

Since it is possible to create the vgic-state file outside of a VM
directory, the file is not cleaned up when a VM is destroyed.
Nonetheless, the corresponding struct kvm is freed when the VM is
destroyed.

Plug the use-after-free by plainly refusing to create vgic-state when
KVM fails to create a VM debugfs dir.

Cc: stable@kernel.org
Fixes: 929f45e32499 ("kvm: no need to check return value of debugfs_create functions")
Signed-off-by: Oliver Upton <oupton@google.com>
---
 arch/arm64/kvm/vgic/vgic-debug.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-debug.c b/arch/arm64/kvm/vgic/vgic-debug.c
index f38c40a76251..cf1364a6fabc 100644
--- a/arch/arm64/kvm/vgic/vgic-debug.c
+++ b/arch/arm64/kvm/vgic/vgic-debug.c
@@ -271,6 +271,9 @@ DEFINE_SEQ_ATTRIBUTE(vgic_debug);
 
 void vgic_debug_init(struct kvm *kvm)
 {
+	if (!kvm->debugfs_dentry)
+		return;
+
 	debugfs_create_file("vgic-state", 0444, kvm->debugfs_dentry, kvm,
 			    &vgic_debug_fops);
 }
-- 
2.35.1.1094.g7c7d902a7c-goog

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)
From: Oliver Upton <oupton@google.com>
To: kvmarm@lists.cs.columbia.edu
Cc: kvm@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	James Morse <james.morse@arm.com>,
	 Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	 linux-arm-kernel@lists.infradead.org,
	Peter Shier <pshier@google.com>,
	 Ricardo Koller <ricarkol@google.com>,
	Reiji Watanabe <reijiw@google.com>,
	 Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	 Oliver Upton <oupton@google.com>,
	stable@kernel.org
Subject: [PATCH 1/4] KVM: arm64: vgic: Don't assume the VM debugfs directory exists
Date: Sat,  2 Apr 2022 17:40:41 +0000	[thread overview]
Message-ID: <20220402174044.2263418-2-oupton@google.com> (raw)
In-Reply-To: <20220402174044.2263418-1-oupton@google.com>

Unfortunately, there is no guarantee that KVM was able to instantiate a
debugfs directory for a particular VM. To that end, KVM shouldn't even
attempt to create new debugfs files in this case. If the specified
parent dentry is NULL, debugfs_create_file() will instantiate files at
the root of debugfs.

Since it is possible to create the vgic-state file outside of a VM
directory, the file is not cleaned up when a VM is destroyed.
Nonetheless, the corresponding struct kvm is freed when the VM is
destroyed.

Plug the use-after-free by plainly refusing to create vgic-state when
KVM fails to create a VM debugfs dir.

Cc: stable@kernel.org
Fixes: 929f45e32499 ("kvm: no need to check return value of debugfs_create functions")
Signed-off-by: Oliver Upton <oupton@google.com>
---
 arch/arm64/kvm/vgic/vgic-debug.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-debug.c b/arch/arm64/kvm/vgic/vgic-debug.c
index f38c40a76251..cf1364a6fabc 100644
--- a/arch/arm64/kvm/vgic/vgic-debug.c
+++ b/arch/arm64/kvm/vgic/vgic-debug.c
@@ -271,6 +271,9 @@ DEFINE_SEQ_ATTRIBUTE(vgic_debug);
 
 void vgic_debug_init(struct kvm *kvm)
 {
+	if (!kvm->debugfs_dentry)
+		return;
+
 	debugfs_create_file("vgic-state", 0444, kvm->debugfs_dentry, kvm,
 			    &vgic_debug_fops);
 }
-- 
2.35.1.1094.g7c7d902a7c-goog


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Oliver Upton <oupton@google.com>
To: kvmarm@lists.cs.columbia.edu
Cc: kvm@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	Peter Shier <pshier@google.com>,
	Ricardo Koller <ricarkol@google.com>,
	Reiji Watanabe <reijiw@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	Oliver Upton <oupton@google.com>,
	stable@kernel.org
Subject: [PATCH 1/4] KVM: arm64: vgic: Don't assume the VM debugfs directory exists
Date: Sat,  2 Apr 2022 17:40:41 +0000	[thread overview]
Message-ID: <20220402174044.2263418-2-oupton@google.com> (raw)
In-Reply-To: <20220402174044.2263418-1-oupton@google.com>

Unfortunately, there is no guarantee that KVM was able to instantiate a
debugfs directory for a particular VM. To that end, KVM shouldn't even
attempt to create new debugfs files in this case. If the specified
parent dentry is NULL, debugfs_create_file() will instantiate files at
the root of debugfs.

Since it is possible to create the vgic-state file outside of a VM
directory, the file is not cleaned up when a VM is destroyed.
Nonetheless, the corresponding struct kvm is freed when the VM is
destroyed.

Plug the use-after-free by plainly refusing to create vgic-state when
KVM fails to create a VM debugfs dir.

Cc: stable@kernel.org
Fixes: 929f45e32499 ("kvm: no need to check return value of debugfs_create functions")
Signed-off-by: Oliver Upton <oupton@google.com>
---
 arch/arm64/kvm/vgic/vgic-debug.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-debug.c b/arch/arm64/kvm/vgic/vgic-debug.c
index f38c40a76251..cf1364a6fabc 100644
--- a/arch/arm64/kvm/vgic/vgic-debug.c
+++ b/arch/arm64/kvm/vgic/vgic-debug.c
@@ -271,6 +271,9 @@ DEFINE_SEQ_ATTRIBUTE(vgic_debug);
 
 void vgic_debug_init(struct kvm *kvm)
 {
+	if (!kvm->debugfs_dentry)
+		return;
+
 	debugfs_create_file("vgic-state", 0444, kvm->debugfs_dentry, kvm,
 			    &vgic_debug_fops);
 }
-- 
2.35.1.1094.g7c7d902a7c-goog


  reply	other threads:[~2022-04-02 17:40 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-02 17:40 [PATCH 0/4] KVM: arm64: Fix use-after-free in debugfs Oliver Upton
2022-04-02 17:40 ` Oliver Upton
2022-04-02 17:40 ` Oliver Upton
2022-04-02 17:40 ` Oliver Upton [this message]
2022-04-02 17:40   ` [PATCH 1/4] KVM: arm64: vgic: Don't assume the VM debugfs directory exists Oliver Upton
2022-04-02 17:40   ` Oliver Upton
2022-04-02 22:39   ` Oliver Upton
2022-04-02 22:39     ` Oliver Upton
2022-04-02 22:39     ` Oliver Upton
2022-04-02 17:40 ` [PATCH 2/4] KVM: Only log about debugfs directory collision once Oliver Upton
2022-04-02 17:40   ` Oliver Upton
2022-04-02 17:40   ` Oliver Upton
2022-04-04 17:33   ` Sean Christopherson
2022-04-04 17:33     ` Sean Christopherson
2022-04-04 17:33     ` Sean Christopherson
2022-04-04 17:57     ` Oliver Upton
2022-04-04 17:57       ` Oliver Upton
2022-04-04 17:57       ` Oliver Upton
2022-04-02 17:40 ` [PATCH 3/4] selftests: KVM: Don't leak GIC FD across dirty log test iterations Oliver Upton
2022-04-02 17:40   ` Oliver Upton
2022-04-02 17:40   ` Oliver Upton
2022-04-02 19:26   ` Jing Zhang
2022-04-02 19:26     ` Jing Zhang
2022-04-02 19:26     ` Jing Zhang
2022-04-02 17:40 ` [PATCH 4/4] selftests: KVM: Free the GIC FD when cleaning up in arch_timer Oliver Upton
2022-04-02 17:40   ` Oliver Upton
2022-04-02 17:40   ` Oliver Upton

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