The ring buffer timestamps are synchronized by two timestamp placeholders.
One is the "before_stamp" and the other is the "write_stamp" (sometimes
referred to as the "after stamp" but only in the comments. These two
stamps are key to knowing how to handle nested events coming in with a
lockless system.

When moving across sub-buffers, the before stamp is updated but the write
stamp is not. There's an effort to put back the before stamp to something
that seems logical in case there's nested events. But as the current event
is about to cross sub-buffers, and so will any new nested event that happens,
updating the before stamp is useless, and could even introduce new race
conditions.

The first event on a sub-buffer simply uses the sub-buffer's timestamp
and keeps a "delta" of zero. The "before_stamp" and "write_stamp" are not
used in the algorithm in this case. There's no reason to try to fix the
before_stamp when this happens.

As a bonus, it removes a cmpxchg() when crossing sub-buffers!

Link: https://lore.kernel.org/linux-trace-kernel/20231211114420.36dde01b@gandalf.local.home

Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: a389d86f

 ("ring-buffer: Have nested events still record running time stamp")
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

The snapshot buffer is to mimic the main buffer so that when a snapshot is
needed, the snapshot and main buffer are swapped. When the snapshot buffer
is allocated, it is set to the minimal size that the ring buffer may be at
and still functional. When it is allocated it becomes the same size as the
main ring buffer, and when the main ring buffer changes in size, it should
do.

Currently, the resize only updates the snapshot buffer if it's used by the
current tracer (ie. the preemptirqsoff tracer). But it needs to be updated
anytime it is allocated.

When changing the size of the main buffer, instead of looking to see if
the current tracer is utilizing the snapshot buffer, just check if it is
allocated to know if it should be updated or not.

Also fix typo in comment just above the code change.

Link: https://lore.kernel.org/linux-trace-kernel/20231210225447.48476a6a@rorschach.local.home

Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: ad909e21

 ("tracing: Add internal tracing_snapshot() functions")
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Reading the ring buffer does a swap of a sub-buffer within the ring buffer
with a empty sub-buffer. This allows the reader to have full access to the
content of the sub-buffer that was swapped out without having to worry
about contention with the writer.

The readers call ring_buffer_alloc_read_page() to allocate a page that
will be used to swap with the ring buffer. When the code is finished with
the reader page, it calls ring_buffer_free_read_page(). Instead of freeing
the page, it stores it as a spare. Then next call to
ring_buffer_alloc_read_page() will return this spare instead of calling
into the memory management system to allocate a new page.

Unfortunately, on freeing of the ring buffer, this spare page is not
freed, and causes a memory leak.

Link: https://lore.kernel.org/linux-trace-kernel/20231210221250.7b9cc83c@rorschach.local.home

Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: 73a757e6

 ("ring-buffer: Return reader page back into existing ring buffer")
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Eventfs uses simple_lookup(), however, it will fail if the name of the
entry is beyond NAME_MAX length. When this error is encountered, eventfs
still tries to create dentries instead of skipping the dentry creation.
When the dentry is attempted to be created in this state d_wait_lookup()
will loop forever, waiting for the lookup to be removed.

Fix eventfs to return the error in simple_lookup() back to the caller
instead of continuing to try to create the dentry.

Link: https://lore.kernel.org/linux-trace-kernel/20231210213534.497-1-beaub@linux.microsoft.com

Fixes: 63940449 ("eventfs: Implement eventfs lookup, read, open functions")
Link: https://lore.kernel.org/linux-trace-kernel/20231208183601.GA46-beaub@linux.microsoft.com/


Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

If a large event was added to the ring buffer that is larger than what the
trace_seq can handle, it just drops the output:

 ~# cat /sys/kernel/tracing/trace
 # tracer: nop
 #
 # entries-in-buffer/entries-written: 2/2   #P:8
 #
 #                                _-----=> irqs-off/BH-disabled
 #                               / _----=> need-resched
 #                              | / _---=> hardirq/softirq
 #                              || / _--=> preempt-depth
 #                              ||| / _-=> migrate-disable
 #                              |||| /     delay
 #           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
 #              | |         |   |||||     |         |
            <...>-859     [001] .....   141.118951: tracing_mark_write           <...>-859     [001] .....   141.148201: tracing_mark_write: 78901234

Instead, catch this case and add some context:

 ~# cat /sys/kernel/tracing/trace
 # tracer: nop
 #
 # entries-in-buffer/entries-written: 2/2   #P:8
 #
 #                                _-----=> irqs-off/BH-disabled
 #                               / _----=> need-resched
 #                              | / _---=> hardirq/softirq
 #                              || / _--=> preempt-depth
 #                              ||| / _-=> migrate-disable
 #                              |||| /     delay
 #           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
 #              | |         |   |||||     |         |
            <...>-852     [001] .....   121.550551: tracing_mark_write[LINE TOO BIG]
            <...>-852     [001] .....   121.550581: tracing_mark_write: 78901234

This now emulates the same output as trace_pipe.

Link: https://lore.kernel.org/linux-trace-kernel/20231209171058.78c1a026@gandalf.local.home



Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

The maximum ring buffer data size is the maximum size of data that can be
recorded on the ring buffer. Events must be smaller than the sub buffer
data size minus any meta data. This size is checked before trying to
allocate from the ring buffer because the allocation assumes that the size
will fit on the sub buffer.

The maximum size was calculated as the size of a sub buffer page (which is
currently PAGE_SIZE minus the sub buffer header) minus the size of the
meta data of an individual event. But it missed the possible adding of a
time stamp for events that are added long enough apart that the event meta
data can't hold the time delta.

When an event is added that is greater than the current BUF_MAX_DATA_SIZE
minus the size of a time stamp, but still less than or equal to
BUF_MAX_DATA_SIZE, the ring buffer would go into an infinite loop, looking
for a page that can hold the event. Luckily, there's a check for this loop
and after 1000 iterations and a warning is emitted and the ring buffer is
disabled. But this should never happen.

This can happen when a large event is added first, or after a long period
where an absolute timestamp is prefixed to the event, increasing its size
by 8 bytes. This passes the check and then goes into the algorithm that
causes the infinite loop.

For events that are the first event on the sub-buffer, it does not need to
add a timestamp, because the sub-buffer itself contains an absolute
timestamp, and adding one is redundant.

The fix is to check if the event is to be the first event on the
sub-buffer, and if it is, then do not add a timestamp.

This also fixes 32 bit adding a timestamp when a read of before_stamp or
write_stamp is interrupted. There's still no need to add that timestamp if
the event is going to be the first event on the sub buffer.

Also, if the buffer has "time_stamp_abs" set, then also check if the
length plus the timestamp is greater than the BUF_MAX_DATA_SIZE.

Link: https://lore.kernel.org/all/20231212104549.58863438@gandalf.local.home/
Link: https://lore.kernel.org/linux-trace-kernel/20231212071837.5fdd6c13@gandalf.local.home
Link: https://lore.kernel.org/linux-trace-kernel/20231212111617.39e02849@gandalf.local.home

Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: a4543a2f ("ring-buffer: Get timestamp after event is allocated")
Fixes: 58fbc3c6

 ("ring-buffer: Consolidate add_timestamp to remove some branches")
Reported-by: Kent Overstreet <kent.overstreet@linux.dev> # (on IRC)
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Since 64 bit cmpxchg() is very expensive on 32bit architectures, the
timestamp used by the ring buffer does some interesting tricks to be able
to still have an atomic 64 bit number. It originally just used 60 bits and
broke it up into two 32 bit words where the extra 2 bits were used for
synchronization. But this was not enough for all use cases, and all 64
bits were required.

The 32bit version of the ring buffer timestamp was then broken up into 3
32bit words using the same counter trick. But one update was not done. The
check to see if the read operation was done without interruption only
checked the first two words and not last one (like it had before this
update). Fix it by making sure all three updates happen without
interruption by comparing the initial counter with the last updated
counter.

Link: https://lore.kernel.org/linux-trace-kernel/20231206100050.3100b7bb@gandalf.local.home

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: f03f2abc

 ("ring-buffer: Have 32 bit time stamps use all 64 bits")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

There's a race where if an event is discarded from the ring buffer and an
interrupt were to happen at that time and insert an event, the time stamp
is still used from the discarded event as an offset. This can screw up the
timings.

If the event is going to be discarded, set the "before_stamp" to zero.
When a new event comes in, it compares the "before_stamp" with the
"write_stamp" and if they are not equal, it will insert an absolute
timestamp. This will prevent the timings from getting out of sync due to
the discarded event.

Link: https://lore.kernel.org/linux-trace-kernel/20231206100244.5130f9b3@gandalf.local.home

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: 6f6be606

 ("ring-buffer: Force before_stamp and write_stamp to be different on discard")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Function trace_buffered_event_disable() is responsible for freeing pages
backing buffered events and this process can run concurrently with
trace_event_buffer_lock_reserve().

The following race is currently possible:

* Function trace_buffered_event_disable() is called on CPU 0. It
  increments trace_buffered_event_cnt on each CPU and waits via
  synchronize_rcu() for each user of trace_buffered_event to complete.

* After synchronize_rcu() is finished, function
  trace_buffered_event_disable() has the exclusive access to
  trace_buffered_event. All counters trace_buffered_event_cnt are at 1
  and all pointers trace_buffered_event are still valid.

* At this point, on a different CPU 1, the execution reaches
  trace_event_buffer_lock_reserve(). The function calls
  preempt_disable_notrace() and only now enters an RCU read-side
  critical section. The function proceeds and reads a still valid
  pointer from trace_buffered_event[CPU1] into the local variable
  "entry". However, it doesn't yet read trace_buffered_event_cnt[CPU1]
  which happens later.

* Function trace_buffered_event_disable() continues. It frees
  trace_buffered_event[CPU1] and decrements
  trace_buffered_event_cnt[CPU1] back to 0.

* Function trace_event_buffer_lock_reserve() continues. It reads and
  increments trace_buffered_event_cnt[CPU1] from 0 to 1. This makes it
  believe that it can use the "entry" that it already obtained but the
  pointer is now invalid and any access results in a use-after-free.

Fix the problem by making a second synchronize_rcu() call after all
trace_buffered_event values are set to NULL. This waits on all potential
users in trace_event_buffer_lock_reserve() that still read a previous
pointer from trace_buffered_event.

Link: https://lore.kernel.org/all/20231127151248.7232-2-petr.pavlu@suse.com/
Link: https://lkml.kernel.org/r/20231205161736.19663-4-petr.pavlu@suse.com

Cc: stable@vger.kernel.org
Fixes: 0fc1b09f

 ("tracing: Use temp buffer when filtering events")
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Function trace_buffered_event_disable() produces an unexpected warning
when the previous call to trace_buffered_event_enable() fails to
allocate pages for buffered events.

The situation can occur as follows:

* The counter trace_buffered_event_ref is at 0.

* The soft mode gets enabled for some event and
  trace_buffered_event_enable() is called. The function increments
  trace_buffered_event_ref to 1 and starts allocating event pages.

* The allocation fails for some page and trace_buffered_event_disable()
  is called for cleanup.

* Function trace_buffered_event_disable() decrements
  trace_buffered_event_ref back to 0, recognizes that it was the last
  use of buffered events and frees all allocated pages.

* The control goes back to trace_buffered_event_enable() which returns.
  The caller of trace_buffered_event_enable() has no information that
  the function actually failed.

* Some time later, the soft mode is disabled for the same event.
  Function trace_buffered_event_disable() is called. It warns on
  "WARN_ON_ONCE(!trace_buffered_event_ref)" and returns.

Buffered events are just an optimization and can handle failures. Make
trace_buffered_event_enable() exit on the first failure and left any
cleanup later to when trace_buffered_event_disable() is called.

Link: https://lore.kernel.org/all/20231127151248.7232-2-petr.pavlu@suse.com/
Link: https://lkml.kernel.org/r/20231205161736.19663-3-petr.pavlu@suse.com

Fixes: 0fc1b09f

 ("tracing: Use temp buffer when filtering events")
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

The following warning appears when using buffered events:

[  203.556451] WARNING: CPU: 53 PID: 10220 at kernel/trace/ring_buffer.c:3912 ring_buffer_discard_commit+0x2eb/0x420
[...]
[  203.670690] CPU: 53 PID: 10220 Comm: stress-ng-sysin Tainted: G            E      6.7.0-rc2-default #4 56e6d0fcf5581e6e51eaaecbdaec2a2338c80f3a
[  203.670704] Hardware name: Intel Corp. GROVEPORT/GROVEPORT, BIOS GVPRCRB1.86B.0016.D04.1705030402 05/03/2017
[  203.670709] RIP: 0010:ring_buffer_discard_commit+0x2eb/0x420
[  203.735721] Code: 4c 8b 4a 50 48 8b 42 48 49 39 c1 0f 84 b3 00 00 00 49 83 e8 01 75 b1 48 8b 42 10 f0 ff 40 08 0f 0b e9 fc fe ff ff f0 ff 47 08 <0f> 0b e9 77 fd ff ff 48 8b 42 10 f0 ff 40 08 0f 0b e9 f5 fe ff ff
[  203.735734] RSP: 0018:ffffb4ae4f7b7d80 EFLAGS: 00010202
[  203.735745] RAX: 0000000000000000 RBX: ffffb4ae4f7b7de0 RCX: ffff8ac10662c000
[  203.735754] RDX: ffff8ac0c750be00 RSI: ffff8ac10662c000 RDI: ffff8ac0c004d400
[  203.781832] RBP: ffff8ac0c039cea0 R08: 0000000000000000 R09: 0000000000000000
[  203.781839] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[  203.781842] R13: ffff8ac10662c000 R14: ffff8ac0c004d400 R15: ffff8ac10662c008
[  203.781846] FS:  00007f4cd8a67740(0000) GS:ffff8ad798880000(0000) knlGS:0000000000000000
[  203.781851] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  203.781855] CR2: 0000559766a74028 CR3: 00000001804c4000 CR4: 00000000001506f0
[  203.781862] Call Trace:
[  203.781870]  <TASK>
[  203.851949]  trace_event_buffer_commit+0x1ea/0x250
[  203.851967]  trace_event_raw_event_sys_enter+0x83/0xe0
[  203.851983]  syscall_trace_enter.isra.0+0x182/0x1a0
[  203.851990]  do_syscall_64+0x3a/0xe0
[  203.852075]  entry_SYSCALL_64_after_hwframe+0x6e/0x76
[  203.852090] RIP: 0033:0x7f4cd870fa77
[  203.982920] Code: 00 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 90 b8 89 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e9 43 0e 00 f7 d8 64 89 01 48
[  203.982932] RSP: 002b:00007fff99717dd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000089
[  203.982942] RAX: ffffffffffffffda RBX: 0000558ea1d7b6f0 RCX: 00007f4cd870fa77
[  203.982948] RDX: 0000000000000000 RSI: 00007fff99717de0 RDI: 0000558ea1d7b6f0
[  203.982957] RBP: 00007fff99717de0 R08: 00007fff997180e0 R09: 00007fff997180e0
[  203.982962] R10: 00007fff997180e0 R11: 0000000000000246 R12: 00007fff99717f40
[  204.049239] R13: 00007fff99718590 R14: 0000558e9f2127a8 R15: 00007fff997180b0
[  204.049256]  </TASK>

For instance, it can be triggered by running these two commands in
parallel:

 $ while true; do
    echo hist:key=id.syscall:val=hitcount > \
      /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger;
  done
 $ stress-ng --sysinfo $(nproc)

The warning indicates that the current ring_buffer_per_cpu is not in the
committing state. It happens because the active ring_buffer_event
doesn't actually come from the ring_buffer_per_cpu but is allocated from
trace_buffered_event.

The bug is in function trace_buffered_event_disable() where the
following normally happens:

* The code invokes disable_trace_buffered_event() via
  smp_call_function_many() and follows it by synchronize_rcu(). This
  increments the per-CPU variable trace_buffered_event_cnt on each
  target CPU and grants trace_buffered_event_disable() the exclusive
  access to the per-CPU variable trace_buffered_event.

* Maintenance is performed on trace_buffered_event, all per-CPU event
  buffers get freed.

* The code invokes enable_trace_buffered_event() via
  smp_call_function_many(). This decrements trace_buffered_event_cnt and
  releases the access to trace_buffered_event.

A problem is that smp_call_function_many() runs a given function on all
target CPUs except on the current one. The following can then occur:

* Task X executing trace_buffered_event_disable() runs on CPU 0.

* The control reaches synchronize_rcu() and the task gets rescheduled on
  another CPU 1.

* The RCU synchronization finishes. At this point,
  trace_buffered_event_disable() has the exclusive access to all
  trace_buffered_event variables except trace_buffered_event[CPU0]
  because trace_buffered_event_cnt[CPU0] is never incremented and if the
  buffer is currently unused, remains set to 0.

* A different task Y is scheduled on CPU 0 and hits a trace event. The
  code in trace_event_buffer_lock_reserve() sees that
  trace_buffered_event_cnt[CPU0] is set to 0 and decides the use the
  buffer provided by trace_buffered_event[CPU0].

* Task X continues its execution in trace_buffered_event_disable(). The
  code incorrectly frees the event buffer pointed by
  trace_buffered_event[CPU0] and resets the variable to NULL.

* Task Y writes event data to the now freed buffer and later detects the
  created inconsistency.

The issue is observable since commit dea49978 ("tracing: Fix warning
in trace_buffered_event_disable()") which moved the call of
trace_buffered_event_disable() in __ftrace_event_enable_disable()
earlier, prior to invoking call->class->reg(.. TRACE_REG_UNREGISTER ..).
The underlying problem in trace_buffered_event_disable() is however
present since the original implementation in commit 0fc1b09f
("tracing: Use temp buffer when filtering events").

Fix the problem by replacing the two smp_call_function_many() calls with
on_each_cpu_mask() which invokes a given callback on all CPUs.

Link: https://lore.kernel.org/all/20231127151248.7232-2-petr.pavlu@suse.com/
Link: https://lkml.kernel.org/r/20231205161736.19663-2-petr.pavlu@suse.com

Cc: stable@vger.kernel.org
Fixes: 0fc1b09f ("tracing: Use temp buffer when filtering events")
Fixes: dea49978

 ("tracing: Fix warning in trace_buffered_event_disable()")
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

It use to be that only the top level instance had a snapshot buffer (for
latency tracers like wakeup and irqsoff). When stopping a tracer in an
instance would not disable the snapshot buffer. This could have some
unintended consequences if the irqsoff tracer is enabled.

Consolidate the tracing_start/stop() with tracing_start/stop_tr() so that
all instances behave the same. The tracing_start/stop() functions will
just call their respective tracing_start/stop_tr() with the global_array
passed in.

Link: https://lkml.kernel.org/r/20231205220011.041220035@goodmis.org

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 6d9b3fa5

 ("tracing: Move tracing_max_latency into trace_array")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

When the ring buffer is being resized, it can cause side effects to the
running tracer. For instance, there's a race with irqsoff tracer that
swaps individual per cpu buffers between the main buffer and the snapshot
buffer. The resize operation modifies the main buffer and then the
snapshot buffer. If a swap happens in between those two operations it will
break the tracer.

Simply stop the running tracer before resizing the buffers and enable it
again when finished.

Link: https://lkml.kernel.org/r/20231205220010.748996423@goodmis.org

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 3928a8a2

 ("ftrace: make work with new ring buffer")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

It use to be that only the top level instance had a snapshot buffer (for
latency tracers like wakeup and irqsoff). The update of the ring buffer
size would check if the instance was the top level and if so, it would
also update the snapshot buffer as it needs to be the same as the main
buffer.

Now that lower level instances also has a snapshot buffer, they too need
to update their snapshot buffer sizes when the main buffer is changed,
otherwise the following can be triggered:

 # cd /sys/kernel/tracing
 # echo 1500 > buffer_size_kb
 # mkdir instances/foo
 # echo irqsoff > instances/foo/current_tracer
 # echo 1000 > instances/foo/buffer_size_kb

Produces:

 WARNING: CPU: 2 PID: 856 at kernel/trace/trace.c:1938 update_max_tr_single.part.0+0x27d/0x320

Which is:

	ret = ring_buffer_swap_cpu(tr->max_buffer.buffer, tr->array_buffer.buffer, cpu);

	if (ret == -EBUSY) {
		[..]
	}

	WARN_ON_ONCE(ret && ret != -EAGAIN && ret != -EBUSY);  <== here

That's because ring_buffer_swap_cpu() has:

	int ret = -EINVAL;

	[..]

	/* At least make sure the two buffers are somewhat the same */
	if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
		goto out;

	[..]
 out:
	return ret;
 }

Instead, update all instances' snapshot buffer sizes when their main
buffer size is updated.

Link: https://lkml.kernel.org/r/20231205220010.454662151@goodmis.org

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 6d9b3fa5

 ("tracing: Move tracing_max_latency into trace_array")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

In order to make sure I get CC'd on tracing changes for which my input
would be relevant, add my name as reviewer of the TRACING subsystem.

Link: https://lore.kernel.org/linux-trace-kernel/20231115155018.8236-1-mathieu.desnoyers@efficios.com



Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Since the locking of the parent->d_inode has been moved outside the
creation of the files and directories (as it use to be locked via a
conditional), add a WARN_ON_ONCE() to the case that it's not locked.

Link: https://lkml.kernel.org/r/20231121231112.853962542@goodmis.org



Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

The eventfs directory is dynamically created via the meta data supplied by
the existing trace events. All files and directories in eventfs has a
parent. Do not allow NULL to be passed into eventfs_start_creating() as
the parent because that should never happen. Warn if it does.

Link: https://lkml.kernel.org/r/20231121231112.693841807@goodmis.org



Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

The both create_file_dentry() and create_dir_dentry() takes a boolean
parameter "lookup", as on lookup the inode_lock should already be taken,
but for dcache_dir_open_wrapper() it is not taken.

There's no reason that the dcache_dir_open_wrapper() can't take the
inode_lock before calling these functions. In fact, it's better if it
does, as the lock can be held throughout both directory and file
creations.

This also simplifies the code, and possibly prevents unexpected race
conditions when the lock is released.

Link: https://lkml.kernel.org/r/20231121231112.528544825@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 5790b1fb

 ("eventfs: Remove eventfs_file and just use eventfs_inode")
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

If memory reclaim happens, it can reclaim file system pages. The file
system pages from eventfs may take the eventfs_mutex on reclaim. This
means that allocation while holding the eventfs_mutex must not call into
filesystem reclaim. A lockdep splat uncovered this.

Link: https://lkml.kernel.org/r/20231121231112.373501894@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 28e12c09 ("eventfs: Save ownership and mode")
Fixes: 5790b1fb

 ("eventfs: Remove eventfs_file and just use eventfs_inode")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

With the call to simple_recursive_removal() on the entire eventfs sub
system when the directory is removed, it performs the d_invalidate on all
the dentries when it is removed. There's no need to do clean ups when a
dentry is being created while the directory is being deleted.

As dentries are cleaned up by the simpler_recursive_removal(), trying to
do d_invalidate() in these functions will cause the dentry to be
invalidated twice, and crash the kernel.

Link: https://lore.kernel.org/all/20231116123016.140576-1-naresh.kamboju@linaro.org/
Link: https://lkml.kernel.org/r/20231120235154.422970988@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 407c6726

 ("eventfs: Use simple_recursive_removal() to clean up dentries")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

The logic to free the eventfs_inode (ei) use to set is_freed and clear the
"dentry" field under the eventfs_mutex. But that changed when a race was
found where the ei->dentry needed to be cleared when the last dput() was
called on it. But there was still logic that checked if ei->dentry was not
NULL and is_freed is set, and would warn if it was.

But since that situation was changed and the ei->dentry isn't cleared
until the last dput() is called on it while the ei->is_freed is set, do
not test for that condition anymore, and change the comments to reflect
that.

Link: https://lkml.kernel.org/r/20231120235154.265826243@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 020010fb

 ("eventfs: Delete eventfs_inode when the last dentry is freed")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Merge tag 'kbuild-fixes-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild fixes from Masahiro Yamada:

 - Fix section mismatch warning messages for riscv and loongarch

 - Remove CONFIG_IA64 left-over from linux/export-internal.h

 - Fix the location of the quotes for UIMAGE_NAME

 - Fix a memory leak bug in Kconfig

* tag 'kbuild-fixes-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kconfig: fix memory leak from range properties
  kbuild: Move the single quotes for image name
  linux/export: clean up the IA-64 KSYM_FUNC macro
  modpost: fix section mismatch message for RELA

Pull irq fix from Borislav Petkov:

 - Flush the translation service tables to prevent unpredictable
   behavior on non-coherent GIC devices

* tag 'irq_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irqchip/gic-v3-its: Flush ITS tables correctly in non-coherent GIC designs

Pull x86 fixes from Borislav Petkov:

 - Ignore invalid x2APIC entries in order to not waste per-CPU data

 - Fix a back-to-back signals handling scenario when shadow stack is in
   use

 - A documentation fix

 - Add Kirill as TDX maintainer

* tag 'x86_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/acpi: Ignore invalid x2APIC entries
  x86/shstk: Delay signal entry SSP write until after user accesses
  x86/Documentation: Indent 'note::' directive for protocol version number note
  MAINTAINERS: Add Intel TDX entry

Pull timer fix from Borislav Petkov:

 - Do the push of pending hrtimers away from a CPU which is being
   offlined earlier in the offlining process in order to prevent a
   deadlock

* tag 'timers_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  hrtimers: Push pending hrtimers away from outgoing CPU earlier

Pull scheduler fixes from Borislav Petkov:

 - Fix virtual runtime calculation when recomputing a sched entity's
   weights

 - Fix wrongly rejected unprivileged poll requests to the cgroup psi
   pressure files

 - Make sure the load balancing is done by only one CPU

* tag 'sched_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Fix the decision for load balance
  sched: psi: fix unprivileged polling against cgroups
  sched/eevdf: Fix vruntime adjustment on reweight

Pull locking fix from Borislav Petkov:

 - Fix a hardcoded futex flags case which lead to one robust futex test
   failure

* tag 'locking_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  futex: Fix hardcoded flags

Pull perf fix from Borislav Petkov:

 - Make sure the context refcount is transferred too when migrating perf
   events

* tag 'perf_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/core: Fix cpuctx refcounting

Pull SCSI fixes from James Bottomley:
 "Seven small fixes, six in drivers and one in sd.

  The sd fix is so large because it changes a struct pointer to a struct
  but otherwise is fairly simple"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: ufs: qcom-ufs: dt-bindings: Document the SM8650 UFS Controller
  scsi: sd: Fix sshdr use in sd_suspend_common()
  scsi: scsi_debug: Delete some bogus error checking
  scsi: scsi_debug: Fix some bugs in sdebug_error_write()
  scsi: ufs: core: Fix racing issue between ufshcd_mcq_abort() and ISR
  scsi: ufs: core: Expand MCQ queue slot to DeviceQueueDepth + 1
  scsi: qla2xxx: Fix system crash due to bad pointer access

Pull parisc fixes from Helge Deller:
 "On parisc we still sometimes need writeable stacks, e.g. if programs
  aren't compiled with gcc-14. To avoid issues with the upcoming
  systemd-254 we therefore have to disable prctl(PR_SET_MDWE) for now
  (for parisc only).

  The other two patches are minor: a bugfix for the soft power-off on
  qemu with 64-bit kernel and prefer strscpy() over strlcpy():

   - Fix power soft-off on qemu

   - Disable prctl(PR_SET_MDWE) since parisc sometimes still needs
     writeable stacks

   - Use strscpy instead of strlcpy in show_cpuinfo()"

* tag 'parisc-for-6.7-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  prctl: Disable prctl(PR_SET_MDWE) on parisc
  parisc/power: Fix power soft-off when running on qemu
  parisc: Replace strlcpy() with strscpy()

Pull xfs fixes from Chandan Babu:

 - Fix deadlock arising due to intent items in AIL not being cleared
   when log recovery fails

 - Fix stale data exposure bug when remapping COW fork extents to data
   fork

 - Fix deadlock when data device flush fails

 - Fix AGFL minimum size calculation

 - Select DEBUG_FS instead of XFS_DEBUG when XFS_ONLINE_SCRUB_STATS is
   selected

 - Fix corruption of log inode's extent count field when NREXT64 feature
   is enabled

* tag 'xfs-6.7-fixes-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  xfs: recovery should not clear di_flushiter unconditionally
  xfs: inode recovery does not validate the recovered inode
  xfs: fix again select in kconfig XFS_ONLINE_SCRUB_STATS
  xfs: fix internal error from AGFL exhaustion
  xfs: up(ic_sema) if flushing data device fails
  xfs: only remap the written blocks in xfs_reflink_end_cow_extent
  XFS: Update MAINTAINERS to catch all XFS documentation
  xfs: abort intent items when recovery intents fail
  xfs: factor out xfs_defer_pending_abort

Pull nfsd fixes from Chuck Lever:

 - Fix several long-standing bugs in the duplicate reply cache

 - Fix a memory leak

* tag 'nfsd-6.7-1' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux:
  NFSD: Fix checksum mismatches in the duplicate reply cache
  NFSD: Fix "start of NFS reply" pointer passed to nfsd_cache_update()
  NFSD: Update nfsd_cache_append() to use xdr_stream
  nfsd: fix file memleak on client_opens_release

Pull smb client fixes from Steve French:

 - multichannel fixes (including a lock ordering fix and an important
   refcounting fix)

 - spnego fix

* tag '6.7-rc1-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: fix lock ordering while disabling multichannel
  cifs: fix leak of iface for primary channel
  cifs: fix check of rc in function generate_smb3signingkey
  cifs: spnego: add ';' in HOST_KEY_LEN

systemd-254 tries to use prctl(PR_SET_MDWE) for it's MemoryDenyWriteExecute
functionality, but fails on parisc which still needs executable stacks in
certain combinations of gcc/glibc/kernel.

Disable prctl(PR_SET_MDWE) by returning -EINVAL for now on parisc, until
userspace has catched up.

Signed-off-by: Helge Deller <deller@gmx.de>
Co-developed-by: Linus Torvalds <torvalds@linux-foundation.org>
Reported-by: Sam James <sam@gentoo.org>
Closes: https://github.com/systemd/systemd/issues/29775


Tested-by: Sam James <sam@gentoo.org>
Link: https://lore.kernel.org/all/875y2jro9a.fsf@gentoo.org/
Cc: <stable@vger.kernel.org> # v6.3+

Merge tag 'for-6.7/dm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper fixes from Mike Snitzer:

 - Various fixes for the DM delay target to address regressions
   introduced during the 6.7 merge window

 - Fixes to both DM bufio and the verity target for no-sleep mode,
   to address sleeping while atomic issues

 - Update DM crypt target in response to the treewide change that
   made MAX_ORDER inclusive

* tag 'for-6.7/dm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
  dm-crypt: start allocating with MAX_ORDER
  dm-verity: don't use blocking calls from tasklets
  dm-bufio: fix no-sleep mode
  dm-delay: avoid duplicate logic
  dm-delay: fix bugs introduced by kthread mode
  dm-delay: fix a race between delay_presuspend and delay_bio

Firmware returns the physical address of the power switch,
so need to use gsc_writel() instead of direct memory access.

Fixes: d0c21947

 ("parisc/power: Add power soft-off when running on qemu")
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org # v6.0+

strlcpy() reads the entire source buffer first. This read may exceed
the destination size limit. This is both inefficient and can lead
to linear read overflows if a source string is not NUL-terminated[1].
Additionally, it returns the size of the source string, not the
resulting size of the destination string. In an effort to remove strlcpy()
completely[2], replace strlcpy() here with strscpy().

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [1]
Link: https://github.com/KSPP/linux/issues/89

 [2]
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Azeem Shaikh <azeemshaikh38@gmail.com>
Cc: linux-parisc@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Helge Deller <deller@gmx.de>

Pull i2c fixes from Wolfram Sang:
 "Revert a not-working conversion to generic recovery for PXA,
  use proper IO accessors for designware, and use proper PM level
  for ocores to allow accessing interrupt providers late"

* tag 'i2c-for-6.7-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: ocores: Move system PM hooks to the NOIRQ phase
  i2c: designware: Fix corrupted memory seen in the ISR
  Revert "i2c: pxa: move to generic GPIO recovery"

Pull turbostat updates from Len Brown:

 - Turbostat features are now table-driven (Rui Zhang)

 - Add support for some new platforms (Sumeet Pawnikar, Rui Zhang)

 - Gracefully run in configs when CPUs are limited (Rui Zhang, Srinivas
   Pandruvada)

 - misc minor fixes

[ This came in during the merge window, but sorting out the signed tag
  took a while, so thus the late merge   - Linus ]

* tag 'turbostat-2023.11.07' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux: (86 commits)
  tools/power turbostat: version 2023.11.07
  tools/power/turbostat: bugfix "--show IPC"
  tools/power/turbostat: Add initial support for LunarLake
  tools/power/turbostat: Add initial support for ArrowLake
  tools/power/turbostat: Add initial support for GrandRidge
  tools/power/turbostat: Add initial support for SierraForest
  tools/power/turbostat: Add initial support for GraniteRapids
  tools/power/turbostat: Add MSR_CORE_C1_RES support for spr_features
  tools/power/turbostat: Move process to root cgroup
  tools/power/turbostat: Handle cgroup v2 cpu limitation
  tools/power/turbostat: Abstrct function for parsing cpu string
  tools/power/turbostat: Handle offlined CPUs in cpu_subset
  tools/power/turbostat: Obey allowed CPUs for system summary
  tools/power/turbostat: Obey allowed CPUs for primary thread/core detection
  tools/power/turbostat: Abstract several functions
  tools/power/turbostat: Obey allowed CPUs during startup
  tools/power/turbostat: Obey allowed CPUs when accessing CPU counters
  tools/power/turbostat: Introduce cpu_allowed_set
  tools/power/turbostat: Remove PC7/PC9 support on ADL/RPL
  tools/power/turbostat: Enable MSR_CORE_C1_RES on recent Intel client platforms
  ...