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vmm: Destroy character devices synchronously.

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This fixes a userland race where bhyveload or bhyve can fail to reuse
a VM name after bhyvectl --destroy has returned.

Reported by:	Michael Dexter
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D35186
This commit is contained in:
John Baldwin 2022-05-20 09:53:43 -07:00
parent 6a968ad5d9
commit 7a0c23da4e
1 changed files with 6 additions and 11 deletions
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17
sys/amd64/vmm/vmm_dev.c
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@ -1052,10 +1052,7 @@ sysctl_vmm_destroy(SYSCTL_HANDLER_ARGS)
}
/*
* The 'cdev' will be destroyed asynchronously when 'si_threadcount'
* goes down to 0 so we should not do it again in the callback.
*
* Setting 'sc->cdev' to NULL is also used to indicate that the VM
* Setting 'sc->cdev' to NULL is used to indicate that the VM
* is scheduled for destruction.
*/
cdev = sc->cdev;
@ -1063,21 +1060,19 @@ sysctl_vmm_destroy(SYSCTL_HANDLER_ARGS)
mtx_unlock(&vmmdev_mtx);
/*
* Schedule all cdevs to be destroyed:
* Destroy all cdevs:
*
* - any new operations on the 'cdev' will return an error (ENXIO).
*
* - when the 'si_threadcount' dwindles down to zero the 'cdev' will
* be destroyed and the callback will be invoked in a taskqueue
* context.
*
* - the 'devmem' cdevs are destroyed before the virtual machine 'cdev'
*/
SLIST_FOREACH(dsc, &sc->devmem, link) {
KASSERT(dsc->cdev != NULL, ("devmem cdev already destroyed"));
destroy_dev_sched_cb(dsc->cdev, devmem_destroy, dsc);
destroy_dev(dsc->cdev);
devmem_destroy(dsc);
}
destroy_dev_sched_cb(cdev, vmmdev_destroy, sc);
destroy_dev(cdev);
vmmdev_destroy(sc);
error = 0;
out: