Merge tag 'trace-v7.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace...

Pull tracing fixes from Steven Rostedt:

 - Fix NULL pointer dereference when matching unloaded module wildcard
   event

   The set_event can take events for modules that have not been loaded
   yet. This is done by writing '<event>:mod:<module>'.

   If '<event>' is not added, then it means to add all events in
   <module>. This wildcard is represented by a NULL pointer. If one were
   to try to remove the same module item with a named event it would
   cause a NULL pointer dereference when comparing the NULL with the
   name in strcmp().

      echo ':mod:kvm' > /sys/kernel/tracing/set_event
      echo '!kvm_ack_irq:mod:kvm' >> /sys/kernel/tracing/set_event

   The above will do a strcmp("kvm_ack_irq", NULL) and crash the kernel.

   Test for NULL (wildcard) before doing the strcmp().

 - Fix event data field race in loading two modules at the same time

   When a module loads, its trace events get registered. The fields of
   the events are also dynamically created and added to the events
   fields list. It also will call a function that will look at all the
   events for updates that need to be done. If two modules load at the
   same time, the one that scans all events and their fields may read
   the one being added as the scan doesn't take the event_mutex. This
   may cause a data race.

   Have the scan take the event_mutex to prevent the race.

* tag 'trace-v7.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing: Fix race between update_event_fields and, event_define_fields
  tracing: Fix NULL pointer dereference in module event cache removal