[PATCH v2 1/4] LoongArch: KVM: Clear device pointer in irqchip destroy callbacks

[Tao Cui <cui.tao@linux.dev>]

From: Tao Cui <cuitao@kylinos.cn>

The destroy callbacks of the four irqchip devices free the device
structure without clearing kvm->arch.{ipi,eiointc,pch_pic,dmsintc},
leaving a dangling pointer.  ops->destroy() is not only called at VM
teardown but also when KVM_CREATE_DEVICE succeeds and the following
anon_inode_getfd() fails (e.g. under RLIMIT_NOFILE); the VM stays
alive, kvm_arch_irqchip_in_kernel() still reports true, and interrupt
injection dereferences the freed device.

Clear the pointer when destroying.

Fixes: c532de5a67a7 ("LoongArch: KVM: Add IPI device support")
Fixes: 2e8b9df82631 ("LoongArch: KVM: Add EIOINTC device support")
Fixes: e785dfacf7e7 ("LoongArch: KVM: Add PCHPIC device support")
Fixes: 229132c309d6 ("LoongArch: KVM: Add DMSINTC device support")
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
---
 arch/loongarch/kvm/intc/dmsintc.c | 1 +
 arch/loongarch/kvm/intc/eiointc.c | 1 +
 arch/loongarch/kvm/intc/ipi.c     | 1 +
 arch/loongarch/kvm/intc/pch_pic.c | 1 +
 4 files changed, 4 insertions(+)

diff --git a/arch/loongarch/kvm/intc/dmsintc.c b/arch/loongarch/kvm/intc/dmsintc.c
index 89f980d867be..41c8b597b5bd 100644
--- a/arch/loongarch/kvm/intc/dmsintc.c
+++ b/arch/loongarch/kvm/intc/dmsintc.c
@@ -166,6 +166,7 @@ static void kvm_dmsintc_destroy(struct kvm_device *dev)
 		return;
 
 	kfree(dev->kvm->arch.dmsintc);
+	dev->kvm->arch.dmsintc = NULL;
 	kfree(dev);
 }
 
diff --git a/arch/loongarch/kvm/intc/eiointc.c b/arch/loongarch/kvm/intc/eiointc.c
index 80f78e07c74a..fe0a1918f26f 100644
--- a/arch/loongarch/kvm/intc/eiointc.c
+++ b/arch/loongarch/kvm/intc/eiointc.c
@@ -675,6 +675,7 @@ static void kvm_eiointc_destroy(struct kvm_device *dev)
 
 	kvm = dev->kvm;
 	eiointc = kvm->arch.eiointc;
+	kvm->arch.eiointc = NULL;
 	mutex_lock(&kvm->slots_lock);
 	kvm_io_bus_unregister_dev(kvm, KVM_IOCSR_BUS, &eiointc->device);
 	kvm_io_bus_unregister_dev(kvm, KVM_IOCSR_BUS, &eiointc->device_vext);
diff --git a/arch/loongarch/kvm/intc/ipi.c b/arch/loongarch/kvm/intc/ipi.c
index 7b333a4a0430..6ee90c10827a 100644
--- a/arch/loongarch/kvm/intc/ipi.c
+++ b/arch/loongarch/kvm/intc/ipi.c
@@ -444,6 +444,7 @@ static void kvm_ipi_destroy(struct kvm_device *dev)
 
 	kvm = dev->kvm;
 	ipi = kvm->arch.ipi;
+	kvm->arch.ipi = NULL;
 	mutex_lock(&kvm->slots_lock);
 	kvm_io_bus_unregister_dev(kvm, KVM_IOCSR_BUS, &ipi->device);
 	mutex_unlock(&kvm->slots_lock);
diff --git a/arch/loongarch/kvm/intc/pch_pic.c b/arch/loongarch/kvm/intc/pch_pic.c
index 2b63b0c2c7ce..62c09b5f3937 100644
--- a/arch/loongarch/kvm/intc/pch_pic.c
+++ b/arch/loongarch/kvm/intc/pch_pic.c
@@ -483,6 +483,7 @@ static void kvm_pch_pic_destroy(struct kvm_device *dev)
 
 	kvm = dev->kvm;
 	s = kvm->arch.pch_pic;
+	kvm->arch.pch_pic = NULL;
 	/* unregister pch pic device and free it's memory */
 	mutex_lock(&kvm->slots_lock);
 	kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS, &s->device);
-- 
2.43.0