Merge tag 'trace-v7.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

b1e00ffa · Linus Torvalds <[email protected]> · 2026-09-06 14:21:24 -07:00

Pull tracing fixes from Steven Rostedt:

 - Fix several tracefs files that did not take the trace_array reference

   A trace instance can be created and destroyed in the tracefs
   "instances" directory via mkdir and rmdir respectively. The instance
   is represented by a trace_array descriptor.

   Most tracefs files pass the trace_array as the private data of the
   inode to the open/read/write functions. Since there is no locking
   between the time a task opens a file and the deletion of the instance
   (and the freeing of the trace_array), each open needs to get a
   reference to the trace_array and each close must remove it.

   An instance can't be removed if there's any reference taken on its
   trace_array. The open function uses trace_array_get() that takes a
   lock (preventing removal of instances) and iterates the list of all
   existing trace_arrays and if it finds a match, it takes the reference
   and releases the lock. If it doesn't find a match, it causes the open
   to return -ENODEV.

   There were some added files that did not take the trace_array
   reference on open that needed to be fixed. Sashiko also correctly
   pointed out that there were some files that took an address of an
   field or element of the trace_array which had a pointer back to the
   trace_array to take its reference on open. But this leaves a slight
   race between referencing this element to get the trace_array as the
   element itself could be freed. To solve this, some helper functions
   were created to look for trace_arrays with this field or element in
   the search so that the element did not have to be dereferenced before
   the trace_array's reference was taken.

 - Add a lock around ftrace_ops initialization

   When a ftrace_ops is first used by ftrace, some internal
   initialization is performed on the ops. But if multiple tasks were
   calling functions that did this initialization, it could race and
   perform doing the initialization more than once, corrupting the
   internal data. Add a lock in the initialization code to prevent this
   from happening.

 - Fix splice reads on mmapped buffers

   The logic in the ring buffer splice code for mmapped buffers is
   supposed to do a copy of the memory as the mapped buffers can't be
   given to splice. But there was an if statement within the copy code
   that would return a -1 if a request for a full page was done and it
   wasn't a partial read. This is because this logic was written before
   mmapped buffers existed and this case didn't make sense at the time.
   For mmapped buffers it makes perfect sense and by returning early can
   drop a lot of pages unnecessarily.

 - Have the persistent ring buffer validation check nr_subbufs

   Sashiko reported that the validation code was relying on the saved
   nr_subbufs to match the calculated nr_pages + 1 and if they were off,
   that the code could cause corruption. Sashiko is correct, and the
   saved nr_subbufs should be validated before assuming it is correct.

 - Do not allow more than one instance with the same name on cmdline

   If an admin were to add more than one trace instances with the same
   name they all would be created, but only the first one would be
   accessible via tracefs. This used to not be allowed but some
   restructuring of code has since made it possible.

 - Fix the race between subbuf resize and trace_pipe_raw readers

   If a task was reading trace_pipe_raw while another task was changing
   the ring buffer subbuf size, it could crash the reader. The
   trace_pipe_raw readers do get their own copy of the page from the
   buffer, but the code needs some restructuring to not have the resize
   of the subbuffers cause issues.

 - Cap the size of the mapped (static) ring buffer nr_pages

   The meta data used for ring buffer mapped buffers is 32 bit in size.
   A normal ring buffer could (in theory) have more than 4 billion
   pages. But this is not allowed by mapped buffers, so enforce it.

* tag 'trace-v7.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Use a macro for static buffer bits
  tracing: Fix comment in tracing_buffers_splice_read()
  ring-buffer: Prevent truncation of nr_pages / nr_subbufs
  ring-buffer: Cap static ring buffer nr_pages
  tracing: Fix subbuf resize races with trace_pipe_raw readers
  tracing: Fix to avoid creating trace instances with duplicate names
  ring-buffer: Add checking nr_subbufs to persistent ring buffer validation
  ring-buffer: Allow splice reads on static buffers
  tracing: Take trace_array reference when opening options file
  ftrace: Synchronize the initialization of ftrace_ops
  ftrace: Take trace_array reference before accessing its ftrace_ops
  tracing: Have show_event_filters/triggers files take trace array ref

Commit

b1e00ffaf91c41eb752a1c200295c9ab7abfae1d

Parents

2beb1b31 · d80e1215

Merge commit. Changes below are compared with the first parent: 2beb1b31.

Changes

10 files changed · +357 −185