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Commit 6bbfb265 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by Marcelo Tosatti
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KVM: fix irqfd assign/deassign race 



I think I see the following (theoretical) race:

During irqfd assign, we drop irqfds lock before we
schedule inject work. Therefore, deassign running
on another CPU could cause shutdown and flush to run
before inject, causing user after free in inject.

A simple fix it to schedule inject under the lock.

Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Acked-by: default avatarGregory Haskins <ghaskins@novell.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent c79bd892

virt/kvm/eventfd.c

+2 −1
Original line number Original line Diff line number Diff line
@@ -218,7 +218,6 @@ kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi) 
	events = file->f_op->poll(file, &irqfd->pt);

	events = file->f_op->poll(file, &irqfd->pt);





	list_add_tail(&irqfd->list, &kvm->irqfds.items);

	list_add_tail(&irqfd->list, &kvm->irqfds.items);

	spin_unlock_irq(&kvm->irqfds.lock);





	/*

	/*

	 * Check if there was an event already pending on the eventfd

	 * Check if there was an event already pending on the eventfd
@@ -227,6 +226,8 @@ kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi) 
	if (events & POLLIN)

	if (events & POLLIN)

		schedule_work(&irqfd->inject);

		schedule_work(&irqfd->inject);





	spin_unlock_irq(&kvm->irqfds.lock);



	/*

	/*

	 * do not drop the file until the irqfd is fully initialized, otherwise

	 * do not drop the file until the irqfd is fully initialized, otherwise

	 * we might race against the POLLHUP

	 * we might race against the POLLHUP