CVE-2024-47748

In the Linux kernel, the following vulnerability has been resolved:

vhost_vdpa: assign irq bypass producer token correctly

We used to call irq_bypass_unregister_producer() in

vhost_vdpa_setup_vq_irq() which is problematic as we don't know if the

token pointer is still valid or not.

Actually, we use the eventfd_ctx as the token so the life cycle of the

token should be bound to the VHOST_SET_VRING_CALL instead of

vhost_vdpa_setup_vq_irq() which could be called by set_status().

Fixing this by setting up irq bypass producer's token when handling

VHOST_SET_VRING_CALL and un-registering the producer before calling

vhost_vring_ioctl() to prevent a possible use after free as eventfd

could have been released in vhost_vring_ioctl(). And such registering

and unregistering will only be done if DRIVER_OK is set.