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![]() Revert KVM's misguided attempt to "fix" a use-after-module-unload bug that was actually due to failure to flush a workqueue, not a lack of module refcounting. Pinning the KVM module until kvm_vm_destroy() doesn't prevent use-after-free due to the module being unloaded, as userspace can invoke delete_module() the instant the last reference to KVM is put, i.e. can cause all KVM code to be unmapped while KVM is actively executing said code. Generally speaking, the many instances of module_put(THIS_MODULE) notwithstanding, outside of a few special paths, a module can never safely put the last reference to itself without creating deadlock, i.e. something external to the module *must* put the last reference. In other words, having VMs grab a reference to the KVM module is futile, pointless, and as evidenced by the now-reverted commit |
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