linux-kernel - [PATCH 5.8 158/177] KVM: fix memory leak in kvm_io_bus_unregister

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Message-Id: <20200915140701.264698297@linuxfoundation.org>
Date:   Tue, 15 Sep 2020 16:13:49 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Rustam Kovhaev <rkovhaev@...il.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        syzbot+f196caa45793d6374707@...kaller.appspotmail.com
Subject: [PATCH 5.8 158/177] KVM: fix memory leak in kvm_io_bus_unregister_dev()

From: Rustam Kovhaev <rkovhaev@...il.com>

commit f65886606c2d3b562716de030706dfe1bea4ed5e upstream.

when kmalloc() fails in kvm_io_bus_unregister_dev(), before removing
the bus, we should iterate over all other devices linked to it and call
kvm_iodevice_destructor() for them

Fixes: 90db10434b16 ("KVM: kvm_io_bus_unregister_dev() should never fail")
Cc: stable@...r.kernel.org
Reported-and-tested-by: syzbot+f196caa45793d6374707@...kaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=f196caa45793d6374707
Signed-off-by: Rustam Kovhaev <rkovhaev@...il.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Message-Id: <20200907185535.233114-1-rkovhaev@...il.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 virt/kvm/kvm_main.c |   21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4269,7 +4269,7 @@ int kvm_io_bus_register_dev(struct kvm *
 void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
 			       struct kvm_io_device *dev)
 {
-	int i;
+	int i, j;
 	struct kvm_io_bus *new_bus, *bus;
 
 	bus = kvm_get_bus(kvm, bus_idx);
@@ -4286,17 +4286,20 @@ void kvm_io_bus_unregister_dev(struct kv
 
 	new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
 			  GFP_KERNEL_ACCOUNT);
-	if (!new_bus)  {
+	if (new_bus) {
+		memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
+		new_bus->dev_count--;
+		memcpy(new_bus->range + i, bus->range + i + 1,
+		       (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
+	} else {
 		pr_err("kvm: failed to shrink bus, removing it completely\n");
-		goto broken;
+		for (j = 0; j < bus->dev_count; j++) {
+			if (j == i)
+				continue;
+			kvm_iodevice_destructor(bus->range[j].dev);
+		}
 	}
 
-	memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
-	new_bus->dev_count--;
-	memcpy(new_bus->range + i, bus->range + i + 1,
-	       (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
-
-broken:
 	rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
 	synchronize_srcu_expedited(&kvm->srcu);
 	kfree(bus);