Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

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

1 files changed, 234 insertions, 0 deletions

diff --git a/Documentation/process/stable-kernel-rules.rst b/Documentation/process/stable-kernel-rules.rst
new file mode 100644
index 000000000..edf90bbe3
--- /dev/null
+++ b/Documentation/process/stable-kernel-rules.rst
@@ -0,0 +1,234 @@
+.. _stable_kernel_rules:
+
+Everything you ever wanted to know about Linux -stable releases
+===============================================================
+
+Rules on what kind of patches are accepted, and which ones are not, into the
+"-stable" tree:
+
+- It or an equivalent fix must already exist in Linux mainline (upstream).
+- It must be obviously correct and tested.
+- It cannot be bigger than 100 lines, with context.
+- It must follow the
+  :ref:`Documentation/process/submitting-patches.rst <submittingpatches>`
+  rules.
+- It must either fix a real bug that bothers people or just add a device ID.
+  To elaborate on the former:
+
+  - It fixes a problem like an oops, a hang, data corruption, a real security
+    issue, a hardware quirk, a build error (but not for things marked
+    CONFIG_BROKEN), or some "oh, that's not good" issue.
+  - Serious issues as reported by a user of a distribution kernel may also
+    be considered if they fix a notable performance or interactivity issue.
+    As these fixes are not as obvious and have a higher risk of a subtle
+    regression they should only be submitted by a distribution kernel
+    maintainer and include an addendum linking to a bugzilla entry if it
+    exists and additional information on the user-visible impact.
+  - No "This could be a problem..." type of things like a "theoretical race
+    condition", unless an explanation of how the bug can be exploited is also
+    provided.
+  - No "trivial" fixes without benefit for users (spelling changes, whitespace
+    cleanups, etc).
+
+
+Procedure for submitting patches to the -stable tree
+----------------------------------------------------
+
+.. note::
+
+   Security patches should not be handled (solely) by the -stable review
+   process but should follow the procedures in
+   :ref:`Documentation/process/security-bugs.rst <securitybugs>`.
+
+There are three options to submit a change to -stable trees:
+
+1. Add a 'stable tag' to the description of a patch you then submit for
+   mainline inclusion.
+2. Ask the stable team to pick up a patch already mainlined.
+3. Submit a patch to the stable team that is equivalent to a change already
+   mainlined.
+
+The sections below describe each of the options in more detail.
+
+:ref:`option_1` is **strongly** preferred, it is the easiest and most common.
+:ref:`option_2` is mainly meant for changes where backporting was not considered
+at the time of submission. :ref:`option_3` is an alternative to the two earlier
+options for cases where a mainlined patch needs adjustments to apply in older
+series (for example due to API changes).
+
+When using option 2 or 3 you can ask for your change to be included in specific
+stable series. When doing so, ensure the fix or an equivalent is applicable,
+submitted, or already present in all newer stable trees still supported. This is
+meant to prevent regressions that users might later encounter on updating, if
+e.g. a fix merged for 5.19-rc1 would be backported to 5.10.y, but not to 5.15.y.
+
+.. _option_1:
+
+Option 1
+********
+
+To have a patch you submit for mainline inclusion later automatically picked up
+for stable trees, add this tag in the sign-off area::
+
+  Cc: stable@vger.kernel.org
+
+Use ``Cc: stable@kernel.org`` instead when fixing unpublished vulnerabilities:
+it reduces the chance of accidentally exposing the fix to the public by way of
+'git send-email', as mails sent to that address are not delivered anywhere.
+
+Once the patch is mainlined it will be applied to the stable tree without
+anything else needing to be done by the author or subsystem maintainer.
+
+To send additional instructions to the stable team, use a shell-style inline
+comment to pass arbitrary or predefined notes:
+
+* Specify any additional patch prerequisites for cherry picking::
+
+    Cc: <stable@vger.kernel.org> # 3.3.x: a1f84a3: sched: Check for idle
+    Cc: <stable@vger.kernel.org> # 3.3.x: 1b9508f: sched: Rate-limit newidle
+    Cc: <stable@vger.kernel.org> # 3.3.x: fd21073: sched: Fix affinity logic
+    Cc: <stable@vger.kernel.org> # 3.3.x
+    Signed-off-by: Ingo Molnar <mingo@elte.hu>
+
+  The tag sequence has the meaning of::
+
+    git cherry-pick a1f84a3
+    git cherry-pick 1b9508f
+    git cherry-pick fd21073
+    git cherry-pick <this commit>
+
+  Note that for a patch series, you do not have to list as prerequisites the
+  patches present in the series itself. For example, if you have the following
+  patch series::
+
+    patch1
+    patch2
+
+  where patch2 depends on patch1, you do not have to list patch1 as
+  prerequisite of patch2 if you have already marked patch1 for stable
+  inclusion.
+
+* Point out kernel version prerequisites::
+
+    Cc: <stable@vger.kernel.org> # 3.3.x
+
+  The tag has the meaning of::
+
+    git cherry-pick <this commit>
+
+  For each "-stable" tree starting with the specified version.
+
+  Note, such tagging is unnecessary if the stable team can derive the
+  appropriate versions from Fixes: tags.
+
+* Delay pick up of patches::
+
+    Cc: <stable@vger.kernel.org> # after -rc3
+
+* Point out known problems::
+
+    Cc: <stable@vger.kernel.org> # see patch description, needs adjustments for <= 6.3
+
+There furthermore is a variant of the stable tag you can use to make the stable
+team's backporting tools (e.g AUTOSEL or scripts that look for commits
+containing a 'Fixes:' tag) ignore a change::
+
+     Cc: <stable+noautosel@kernel.org> # reason goes here, and must be present
+
+.. _option_2:
+
+Option 2
+********
+
+If the patch already has been merged to mainline, send an email to
+stable@vger.kernel.org containing the subject of the patch, the commit ID,
+why you think it should be applied, and what kernel versions you wish it to
+be applied to.
+
+.. _option_3:
+
+Option 3
+********
+
+Send the patch, after verifying that it follows the above rules, to
+stable@vger.kernel.org and mention the kernel versions you wish it to be applied
+to. When doing so, you must note the upstream commit ID in the changelog of your
+submission with a separate line above the commit text, like this::
+
+  commit <sha1> upstream.
+
+Or alternatively::
+
+  [ Upstream commit <sha1> ]
+
+If the submitted patch deviates from the original upstream patch (for example
+because it had to be adjusted for the older API), this must be very clearly
+documented and justified in the patch description.
+
+
+Following the submission
+------------------------
+
+The sender will receive an ACK when the patch has been accepted into the
+queue, or a NAK if the patch is rejected.  This response might take a few
+days, according to the schedules of the stable team members.
+
+If accepted, the patch will be added to the -stable queue, for review by other
+developers and by the relevant subsystem maintainer.
+
+
+Review cycle
+------------
+
+- When the -stable maintainers decide for a review cycle, the patches will be
+  sent to the review committee, and the maintainer of the affected area of
+  the patch (unless the submitter is the maintainer of the area) and CC: to
+  the linux-kernel mailing list.
+- The review committee has 48 hours in which to ACK or NAK the patch.
+- If the patch is rejected by a member of the committee, or linux-kernel
+  members object to the patch, bringing up issues that the maintainers and
+  members did not realize, the patch will be dropped from the queue.
+- The ACKed patches will be posted again as part of release candidate (-rc)
+  to be tested by developers and testers.
+- Usually only one -rc release is made, however if there are any outstanding
+  issues, some patches may be modified or dropped or additional patches may
+  be queued. Additional -rc releases are then released and tested until no
+  issues are found.
+- Responding to the -rc releases can be done on the mailing list by sending
+  a "Tested-by:" email with any testing information desired. The "Tested-by:"
+  tags will be collected and added to the release commit.
+- At the end of the review cycle, the new -stable release will be released
+  containing all the queued and tested patches.
+- Security patches will be accepted into the -stable tree directly from the
+  security kernel team, and not go through the normal review cycle.
+  Contact the kernel security team for more details on this procedure.
+
+
+Trees
+-----
+
+- The queues of patches, for both completed versions and in progress
+  versions can be found at:
+
+    https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git
+
+- The finalized and tagged releases of all stable kernels can be found
+  in separate branches per version at:
+
+    https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
+
+- The release candidate of all stable kernel versions can be found at:
+
+    https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/
+
+  .. warning::
+     The -stable-rc tree is a snapshot in time of the stable-queue tree and
+     will change frequently, hence will be rebased often. It should only be
+     used for testing purposes (e.g. to be consumed by CI systems).
+
+
+Review committee
+----------------
+
+- This is made up of a number of kernel developers who have volunteered for
+  this task, and a few that haven't.