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

This is another run of the Coccinelle script for converting kmalloc()
family of allocations to kmalloc_obj() via the existing rules in
scripts/coccinelle/api/kmalloc_objs.cocci

This catches both the set of kmalloc() uses added since the first
kmalloc_obj() conversions in v7.0 and adds a large group missed in the
first pass due to Coccinelle not interacting well with the cleanup.h
scoped_...() family of macros[1]. I worked around this with spatch's
"--macro-file" argument to a file with all the scoped_...() macros mapped
to Coccinelle's YACFE_ITERATOR[2] as that was the closest viable control
flow indicator I could find.

Build tested allmodconfig on x86, arm64, arm, loongarch, mips, powerpc,
riscv, and s390 with no new warnings.

Link: https://lore.kernel.org/lkml/202609021314.8A9C0B8@keescook/ [1]
Link: https://github.com/coccinelle/coccinelle/blob/master/standard.h [2]
Signed-off-by: Kees Cook <kees+treewide@kernel.org>

Instead of hard coding 30 for the number of bits used for the static
buffer ids in two places, create a macro. This way if it changes in the
future, it will change in all the locations that use it.

Link: https://patch.msgid.link/20260904151641.17eae0aa@gandalf.local.home
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Although ring_buffer_per_cpu::nr_pages is defined as unsigned long, it
is capped to 32-bits in a few places, limiting the operations possible
on a very large buffer. Use `unsigned long` where appropriate and
prevent truncation of values using nr_pages (or nr_subbufs).

While at it, subbuf_size must be at least `unsigned int`.

Note that persistent, remote and user-mapped ring buffers are capping
the number of pages to 30 bits already, making "int" safe in many
places.

Link: https://patch.msgid.link/20260904164450.1345852-5-vdonnefort@google.com
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Static ring buffers (i.e. persistent, user-mapped and remote) rely on
the bpage::id field. The number of pages for those ring buffers must fit
into that variable. Enforce this limit on ring buffer creation or
user-mapping.

While at it, prevent nr_pages underflow when allocating a persistent
buffer.

Link: https://patch.msgid.link/20260904164450.1345852-4-vdonnefort@google.com
Fixes: be68d63a139b ("ring-buffer: Add ring_buffer_alloc_range()")
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Concurrent subbuffer resizes may crash trace_pipe_raw readers or leak
uninitialized memory to userspace due to stale size values.

Modify ring_buffer_alloc_read_page() to handle the resizing of an
existing buffer_data_read_page if necessary and add a new
ring_buffer_read_page_size(). This new function enables ring-buffer
buffer_data_read_page users to not call the racy
ring_buffer_subbuf_size_get(). This makes the spare_size member of
ftrace_buffer_info redundant.

Finally, handle buffer_data_read_page/reader_page order discrepancy in
ring_buffer_read_page(). On a mismatch simply copy manually the data to
the buffer_data_read_page.

Link: https://lore.kernel.org/all/20260817140812.2C7D41F00A3A@smtp.kernel.org/
Link: https://patch.msgid.link/20260904164450.1345852-3-vdonnefort@google.com
Fixes: bce761d75745 ("ring-buffer: Read and write to ring buffers with custom sub buffer size")
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Sashiko reported that the code was using meta->nr_subbufs without making
sure that it matched the nr_pages + 1 on data that was assuming the two
were the same.

Add a check to the persistent ring buffer validation code to make sure
that the saved nr_subbufs matches what we expect.

Link: https://patch.msgid.link/20260903132728.7fb27d34@gandalf.local.home
Fixes: f5b95f1fa2ef3 ("ring-buffer: Validate the persistent meta data subbuf array")
Reported-by: sashiko-bot@kernel.org
Closes: https://lore.kernel.org/all/20260901164836.D962D1F000E9@smtp.kernel.org/
Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

ring_buffer_read_page() rejects splice (full=1) reads on static buffers
(that is user-mapped, persistent or remote) because !read check assumes
unread pages must be swapped. However for those buffers we have no other
choice than memcpy the data.

For the memcpy case, only return an error when the writer is still on
the reader page for the splice interface to wait.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260901155445.1475405-2-vdonnefort@google.com
Fixes: 117c39200d9d ("ring-buffer: Introducing ring-buffer mapping functions")
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

The remote swap_reader_page callback can return -EBUSY when the writer
moves the head before the remote catches it, particularly during an event
storm on a small buffer. __rb_get_reader_page_from_remote() currently
warns about that failure but continues with the unchanged reader ID and
rearranges the local page list as though the swap succeeded.

Handle the callback failure as a recoverable error. Report it with
pr_warn_ratelimited() and return NULL. Callers already handle a NULL reader
page as a failed attempt. This avoids splicing the same page as both the
previous and new reader without flooding the log under contention.

Cc: stable@vger.kernel.org
Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes")
Link: https://patch.msgid.link/20260825-kernel-patch-1-v2-2-bb3461807a32@gmail.com
Assisted-by: LLM sparse
Signed-off-by: Ivan Immanuel Shaji <ivanimmanuel1234@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>