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| author | Paolo Bonzini <pbonzini@redhat.com> | 2018-05-28 13:31:13 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2018-07-18 11:31:27 +0200 |
| commit | 9432a3175770e06cb83eada2d91fac90c977cb99 (patch) | |
| tree | 13f5e44fdcc83b3b5fdc7607290064130af84853 | |
| parent | b5020a8e6b54d2ece80b1e7dedb33c79a40ebd47 (diff) | |
| download | op-kernel-dev-9432a3175770e06cb83eada2d91fac90c977cb99.zip op-kernel-dev-9432a3175770e06cb83eada2d91fac90c977cb99.tar.gz | |
KVM: irqfd: fix race between EPOLLHUP and irq_bypass_register_consumer
A comment warning against this bug is there, but the code is not doing what
the comment says. Therefore it is possible that an EPOLLHUP races against
irq_bypass_register_consumer. The EPOLLHUP handler schedules irqfd_shutdown,
and if that runs soon enough, you get a use-after-free.
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
| -rw-r--r-- | virt/kvm/eventfd.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index decefe9..fe6eb0f 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -405,11 +405,6 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) if (events & EPOLLIN) schedule_work(&irqfd->inject); - /* - * do not drop the file until the irqfd is fully initialized, otherwise - * we might race against the EPOLLHUP - */ - fdput(f); #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS if (kvm_arch_has_irq_bypass()) { irqfd->consumer.token = (void *)irqfd->eventfd; @@ -425,6 +420,12 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) #endif srcu_read_unlock(&kvm->irq_srcu, idx); + + /* + * do not drop the file until the irqfd is fully initialized, otherwise + * we might race against the EPOLLHUP + */ + fdput(f); return 0; fail: |
