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Message-Id: <20210512144831.428979450@linuxfoundation.org>
Date: Wed, 12 May 2021 16:43:06 +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, Sean Christopherson <seanjc@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 5.11 109/601] KVM: Destroy I/O bus devices on unregister failure _after_ syncing SRCU
From: Sean Christopherson <seanjc@...gle.com>
commit 2ee3757424be7c1cd1d0bbfa6db29a7edd82a250 upstream.
If allocating a new instance of an I/O bus fails when unregistering a
device, wait to destroy the device until after all readers are guaranteed
to see the new null bus. Destroying devices before the bus is nullified
could lead to use-after-free since readers expect the devices on their
reference of the bus to remain valid.
Fixes: f65886606c2d ("KVM: fix memory leak in kvm_io_bus_unregister_dev()")
Cc: stable@...r.kernel.org
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Message-Id: <20210412222050.876100-2-seanjc@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
virt/kvm/kvm_main.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4487,7 +4487,13 @@ void kvm_io_bus_unregister_dev(struct kv
new_bus->dev_count--;
memcpy(new_bus->range + i, bus->range + i + 1,
flex_array_size(new_bus, range, new_bus->dev_count - i));
- } else {
+ }
+
+ rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
+ synchronize_srcu_expedited(&kvm->srcu);
+
+ /* Destroy the old bus _after_ installing the (null) bus. */
+ if (!new_bus) {
pr_err("kvm: failed to shrink bus, removing it completely\n");
for (j = 0; j < bus->dev_count; j++) {
if (j == i)
@@ -4496,8 +4502,6 @@ void kvm_io_bus_unregister_dev(struct kv
}
}
- rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
- synchronize_srcu_expedited(&kvm->srcu);
kfree(bus);
return;
}
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