• Philippe Gerum's avatar
    cobalt/registry: fix export/unexport race on object deletion · 997b8e18
    Philippe Gerum authored
    Running xnregistry_enter() then xnregistry_remove() in quick
    succession for the same object might cause the latter to NULLify the
    objaddr field while proc_callback() is busy calling the vfile export
    handler for the object, which is going to use that same value,
    certainly leading to a crash.
    
    This bug is due to the asynchronous nature of the vfile
    export/unexport process which is deferred to a regular workqueue on
    the root stage when kicked from the head stage.
    
    Fix this by adding a third logic state describing an aborted vfile
    export procedure, due to handling an object removal request while the
    workqueue is concurrently running for the same object. In addition,
    since an exported object might be stale before it is considered for
    export, do not anticipate on the next object to process in
    proc_callback() as list_for_each_entry_safe() would do, but always
    pick the list head under lock.
    
    At this chance, clarify the naming of the magic vfile values
    enumerating those states (i.e. XNOBJECT_EXPORT_xxx).
    Signed-off-by: Philippe Gerum's avatarPhilippe Gerum <rpm@xenomai.org>
    Signed-off-by: Jan Kiszka's avatarJan Kiszka <jan.kiszka@siemens.com>
    997b8e18
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