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authorPaolo Bonzini <pbonzini@redhat.com>2018-05-28 13:31:13 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-08-24 13:09:21 +0200
commit270d5d77191769eaa57f94eff3ef8119121a091a (patch)
tree273263dc89891d0375fbbf755a0806cc6434d045 /virt
parent7a12f4ed07a5f7b49c7d4f86ea67f65ec953cc40 (diff)
KVM: irqfd: fix race between EPOLLHUP and irq_bypass_register_consumer
commit 9432a3175770e06cb83eada2d91fac90c977cb99 upstream. 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> Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/eventfd.c11
1 files changed, 6 insertions, 5 deletions
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 58a9b31b0dd5..088734a700e9 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 & POLLIN)
schedule_work(&irqfd->inject);
- /*
- * do not drop the file until the irqfd is fully initialized, otherwise
- * we might race against the POLLHUP
- */
- 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 POLLHUP
+ */
+ fdput(f);
return 0;
fail: