Subject: CVE-2022-48848: tracing/osnoise: Do not unregister events twice

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

tracing/osnoise: Do not unregister events twice

Nicolas reported that using:

 # trace-cmd record -e all -M 10 -p osnoise --poll

Resulted in the following kernel warning:

 ------------[ cut here ]------------
 WARNING: CPU: 0 PID: 1217 at kernel/tracepoint.c:404 tracepoint_probe_unregister+0x280/0x370
 [...]
 CPU: 0 PID: 1217 Comm: trace-cmd Not tainted 5.17.0-rc6-next-20220307-nico+ #19
 RIP: 0010:tracepoint_probe_unregister+0x280/0x370
 [...]
 CR2: 00007ff919b29497 CR3: 0000000109da4005 CR4: 0000000000170ef0
 Call Trace:
  <TASK>
  osnoise_workload_stop+0x36/0x90
  tracing_set_tracer+0x108/0x260
  tracing_set_trace_write+0x94/0xd0
  ? __check_object_size.part.0+0x10a/0x150
  ? selinux_file_permission+0x104/0x150
  vfs_write+0xb5/0x290
  ksys_write+0x5f/0xe0
  do_syscall_64+0x3b/0x90
  entry_SYSCALL_64_after_hwframe+0x44/0xae
 RIP: 0033:0x7ff919a18127
 [...]
 ---[ end trace 0000000000000000 ]---

The warning complains about an attempt to unregister an
unregistered tracepoint.

This happens on trace-cmd because it first stops tracing, and
then switches the tracer to nop. Which is equivalent to:

  # cd /sys/kernel/tracing/
  # echo osnoise > current_tracer
  # echo 0 > tracing_on
  # echo nop > current_tracer

The osnoise tracer stops the workload when no trace instance
is actually collecting data. This can be caused both by
disabling tracing or disabling the tracer itself.

To avoid unregistering events twice, use the existing
trace_osnoise_callback_enabled variable to check if the events
(and the workload) are actually active before trying to
deactivate them.

The Linux kernel CVE team has assigned CVE-2022-48848 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.16 with commit 2fac8d6486d5 and fixed in 5.16.15 with commit 4e10787d1837
	Issue introduced in 5.16 with commit 2fac8d6486d5 and fixed in 5.17 with commit f0cfe17bcc1d

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-48848
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	kernel/trace/trace_osnoise.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/4e10787d18379d9b296290c2288097feddef16d4
	https://git.kernel.org/stable/c/f0cfe17bcc1dd2f0872966b554a148e888833ee9