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| author | Lan Tianyu <tianyu.lan@intel.com> | 2017-12-21 21:10:36 -0500 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2018-07-18 11:31:27 +0200 |
| commit | b5020a8e6b54d2ece80b1e7dedb33c79a40ebd47 (patch) | |
| tree | 100e74e7b047f3076e13acc86567cf924c0f83e1 /virt | |
| parent | 94ffba484663ab3fc695ce2a34871e8c3db499f7 (diff) | |
| download | lwn-b5020a8e6b54d2ece80b1e7dedb33c79a40ebd47.tar.gz lwn-b5020a8e6b54d2ece80b1e7dedb33c79a40ebd47.zip | |
KVM/Eventfd: Avoid crash when assign and deassign specific eventfd in parallel.
Syzbot reports crashes in kvm_irqfd_assign(), caused by use-after-free
when kvm_irqfd_assign() and kvm_irqfd_deassign() run in parallel
for one specific eventfd. When the assign path hasn't finished but irqfd
has been added to kvm->irqfds.items list, another thead may deassign the
eventfd and free struct kvm_kernel_irqfd(). The assign path then uses
the struct kvm_kernel_irqfd that has been freed by deassign path. To avoid
such issue, keep irqfd under kvm->irq_srcu protection after the irqfd
has been added to kvm->irqfds.items list, and call synchronize_srcu()
in irq_shutdown() to make sure that irqfd has been fully initialized in
the assign path.
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Tianyu Lan <tianyu.lan@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt')
| -rw-r--r-- | virt/kvm/eventfd.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index 6e865e8b5b10..decefe944b0f 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -119,8 +119,12 @@ irqfd_shutdown(struct work_struct *work) { struct kvm_kernel_irqfd *irqfd = container_of(work, struct kvm_kernel_irqfd, shutdown); + struct kvm *kvm = irqfd->kvm; u64 cnt; + /* Make sure irqfd has been initalized in assign path. */ + synchronize_srcu(&kvm->irq_srcu); + /* * Synchronize with the wait-queue and unhook ourselves to prevent * further events. @@ -387,7 +391,6 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) idx = srcu_read_lock(&kvm->irq_srcu); irqfd_update(kvm, irqfd); - srcu_read_unlock(&kvm->irq_srcu, idx); list_add_tail(&irqfd->list, &kvm->irqfds.items); @@ -421,6 +424,7 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) } #endif + srcu_read_unlock(&kvm->irq_srcu, idx); return 0; fail: |