The point of using set_child_tid to hold the kthread pointer was that
it already did what is necessary.  There are now restrictions on when
set_child_tid can be initialized and when set_child_tid can be used in
schedule_tail.  Which indicates that continuing to use set_child_tid
to hold the kthread pointer is a bad idea.

Instead of continuing to use the set_child_tid field of task_struct
generalize the pf_io_worker field of task_struct and use it to hold
the kthread pointer.

Rename pf_io_worker (which is a void * pointer) to worker_private so
it can be used to store kthreads struct kthread pointer.  Update the
kthread code to store the kthread pointer in the worker_private field.
Remove the places where set_child_tid had to be dealt with carefully
because kthreads also used it.

Link: https://lkml.kernel.org/r/CAHk-=wgtFAA9SbVYg0gR1tqPMC17-NYcs0GQkaYg1bGhh1uJQQ@mail.gmail.com
Link: https://lkml.kernel.org/r/87a6grvqy8.fsf_-_@email.froward.int.ebiederm.orgSuggested-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Kernel threads abuse set_child_tid.  Historically that has been fine
as set_child_tid was initialized after the kernel thread had been
forked.  Unfortunately storing struct kthread in set_child_tid after
the thread is running makes struct kthread being unusable for storing
result codes of the thread.

When set_child_tid is set to struct kthread during fork that results
in schedule_tail writing the thread id to the beggining of struct
kthread (if put_user does not realize it is a kernel address).

Solve this by skipping the put_user for all kthreads.
Reported-by: NNathan Chancellor <nathan@kernel.org>
Link: https://lkml.kernel.org/r/YcNsG0Lp94V13whH@archlinux-ax161Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Failed allocates are not expected when setting up the initial task and
it is not really possible to handle them either.  So I added a warning
to report if such an allocation failure ever happens.

Correct the sense of the warning so it warns when an allocation failure
happens not when the allocation succeeded.  Oops.
Reported-by: Nkernel test robot <oliver.sang@intel.com>
Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Reported-by: NNaresh Kamboju <naresh.kamboju@linaro.org>
Link: https://lkml.kernel.org/r/20211221231611.785b74cf@canb.auug.org.au
Link: https://lkml.kernel.org/r/CA+G9fYvLaR5CF777CKeWTO+qJFTN6vAvm95gtzN+7fw3Wi5hkA@mail.gmail.com
Link: https://lkml.kernel.org/r/20211216102956.GC10708@xsang-OptiPlex-9020
Fixes: 40966e31 ("kthread: Ensure struct kthread is present for all kthreads")
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

I just fixed a bug in copy_process when using the label
bad_fork_cleanup_threadgroup_lock.  While fixing the bug I looked
closer at the label and realized it has been misnamed since
568ac888 ("cgroup: reduce read locked section of
cgroup_threadgroup_rwsem during fork").

Fix the name so that fork is easier to understand.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Mark Brown <broonie@kernel.org> reported:

> This is also causing further build errors including but not limited to:
>
> /tmp/next/build/kernel/fork.c: In function 'copy_process':
> /tmp/next/build/kernel/fork.c:2106:4: error: label 'bad_fork_cleanup_threadgroup_lock' used but not defined
>  2106 |    goto bad_fork_cleanup_threadgroup_lock;
>       |    ^~~~

It turns out that I messed up and was depending upon a label protected
by an ifdef.  Move the label out of the ifdef as the ifdef around the label
no longer makes sense (if it ever did).

Link: https://lkml.kernel.org/r/YbugCP144uxXvRsk@sirena.org.uk
Fixes: 40966e31 ("kthread: Ensure struct kthread is present for all kthreads")
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Recently the kbuild robot reported two new errors:

>> lib/kunit/kunit-example-test.o: warning: objtool: .text.unlikely: unexpected end of section
>> arch/x86/kernel/dumpstack.o: warning: objtool: oops_end() falls through to next function show_opcodes()

I don't know why they did not occur in my test setup but after digging
it I realized I had accidentally dropped a comma in
tools/objtool/check.c when I renamed rewind_stack_do_exit to
rewind_stack_and_make_dead.

Add that comma back to fix objtool errors.

Link: https://lkml.kernel.org/r/202112140949.Uq5sFKR1-lkp@intel.com
Fixes: 0e25498f ("exit: Add and use make_task_dead.")
Reported-by: Nkernel test robot <lkp@intel.com>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

I misspelled kthread_complete_and_exit in the kernel doc comment fix
it.

Link: https://lkml.kernel.org/r/202112141329.KBkyJ5ql-lkp@intel.com
Link: https://lkml.kernel.org/r/202112141422.Cykr6YUS-lkp@intel.comReported-by: Nkernel test robot <lkp@intel.com>
Fixes: cead1855 ("exit: Rename complete_and_exit to kthread_complete_and_exit")
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

The exit code of kernel threads has different semantics than the
exit_code of userspace tasks.  To avoid confusion and allow
the userspace implementation to change as needed move
the kernel thread exit code into struct kthread.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Today the rules are a bit iffy and arbitrary about which kernel
threads have struct kthread present.  Both idle threads and thread
started with create_kthread want struct kthread present so that is
effectively all kernel threads.  Make the rule that if PF_KTHREAD
and the task is running then struct kthread is present.

This will allow the kernel thread code to using tsk->exit_code
with different semantics from ordinary processes.

To make ensure that struct kthread is present for all
kernel threads move it's allocation into copy_process.

Add a deallocation of struct kthread in exec for processes
that were kernel threads.

Move the allocation of struct kthread for the initial thread
earlier so that it is not repeated for each additional idle
thread.

Move the initialization of struct kthread into set_kthread_struct
so that the structure is always and reliably initailized.

Clear set_child_tid in free_kthread_struct to ensure the kthread
struct is reliably freed during exec.  The function
free_kthread_struct does not need to clear vfork_done during exec as
exec_mm_release called from exec_mmap has already cleared vfork_done.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Update complete_and_exit to call kthread_exit instead of do_exit.

Change the name to reflect this change in functionality.  All of the
users of complete_and_exit are causing the current kthread to exit so
this change makes it clear what is happening.

Move the implementation of kthread_complete_and_exit from
kernel/exit.c to to kernel/kthread.c.  As this function is kthread
specific it makes most sense to live with the kthread functions.

There are no functional change.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Update module_put_and_exit to call kthread_exit instead of do_exit.

Change the name to reflect this change in functionality.  All of the
users of module_put_and_exit are causing the current kthread to exit
so this change makes it clear what is happening.  There is no
functional change.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

The way the per task_struct exit_code is used by kernel threads is not
quite compatible how it is used by userspace applications.  The low
byte of the userspace exit_code value encodes the exit signal.  While
kthreads just use the value as an int holding ordinary kernel function
exit status like -EPERM.

Add kthread_exit to clearly separate the two kinds of uses.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Now that there are no more modular uses of do_exit remove the EXPORT_SYMBOL.
Suggested-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

When the kernel detects it is oops or otherwise force killing a task
while it exits the code poorly attempts to permanently stop the task
from scheduling.

I say poorly because it is possible for a task in TASK_UINTERRUPTIBLE
to be woken up.

As it makes no sense for the task to continue call do_task_dead
instead which actually does the work and permanently removes the task
from the scheduler.  Guaranteeing the task will never be woken
up again.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

The beginning of do_exit has become cluttered and difficult to read as
it is filled with checks to handle things that can only happen when
the kernel is operating improperly.

Now that we have a dedicated function for cleaning up a task when the
kernel is operating improperly move the checks there.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

There are two big uses of do_exit.  The first is it's design use to be
the guts of the exit(2) system call.  The second use is to terminate
a task after something catastrophic has happened like a NULL pointer
in kernel code.

Add a function make_task_dead that is initialy exactly the same as
do_exit to cover the cases where do_exit is called to handle
catastrophic failure.  In time this can probably be reduced to just a
light wrapper around do_task_dead. For now keep it exactly the same so
that there will be no behavioral differences introducing this new
concept.

Replace all of the uses of do_exit that use it for catastraphic
task cleanup with make_task_dead to make it clear what the code
is doing.

As part of this rename rewind_stack_do_exit
rewind_stack_and_make_dead.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

My s390 assembly is not particularly good so I have read the history
of the reference to do_exit copy_thread and have been able to
verify that do_exit is not used.

The general argument is that s390 has been changed to use the generic
kernel_thread and kernel_execve and the generic versions do not call
do_exit.  So it is strange to see a do_exit reference sitting there.

The history of the do_exit reference in s390's version of copy_thread
seems conclusive that the do_exit reference is something that lingers
and should have been removed several years ago.

Up through 8d19f15a60be ("[PATCH] s390 update (1/27): arch.")  the
s390 code made a call to the exit(2) system call when a kernel thread
finished.  Then kernel_thread_starter was added which branched
directly to the value in register 11 when the kernel thread finshed.
The value in register 11 was set in kernel_thread to
"regs.gprs[11] = (unsigned long) do_exit"

In commit 37fe5d41 ("s390: fold kernel_thread_helper() into
ret_from_fork()") kernel_thread_starter was moved into entry.S and
entry64.S unchanged (except for the syntax differences between inline
assemly and in the assembly file).

In commit f9a7e025 ("s390: switch to generic kernel_thread()") the
assignment to "gprs[11]" was moved into copy_thread from the old
kernel_thread.  The helper kernel_thread_starter was still being used
and was still branching to "%r11" at the end.

In commit 30dcb099 ("s390: switch to saner kernel_execve()
semantics") kernel_thread_starter was changed to unconditionally
branch to sysc_tracenogo instead to %r11 which held the value of
do_exit.  Unfortunately copy_thread was not updated to stop passing
do_exit in "gprs[11]".

In commit 56e62a73 ("s390: convert to generic entry")
kernel_thread_starter was replaced by __ret_from_fork.  And the code
still continued to pass do_exit in "gprs[11]" despite __ret_from_fork
not caring in the slightest.

Remove this dead reference to do_exit to make it clear that s390 is
not doing anything with do_exit in copy_thread.

Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Fixes: 30dcb099 ("s390: switch to saner kernel_execve() semantics")
History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.gitAcked-by: NHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

I completed the first batch of signal changes for v5.17 against
v5.16-rc1 before the SA_IMMUTABLE fixes where completed.  Which leaves
me with two lines of development that I want on my signal development
branch both rooted at v5.16-rc1.  Especially as I am hoping
to reach the point of being able to remove SA_IMMUTABLE.

Linus merged my SA_IMUTABLE fixes as:
7af959b5 ("Merge branch 'SA_IMMUTABLE-fixes-for-v5.16-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace")

To avoid rebasing the development changes that are currently complete I am
merging the work I sent upstream to Linus to make my life simpler.

The SA_IMMUTABLE changes as they are described in Linus's merge commit.

Pull exit-vs-signal handling fixes from Eric Biederman:
 "This is a small set of changes where debuggers were no longer able to
  intercept synchronous SIGTRAP and SIGSEGV, introduced by the exit
  cleanups.

  This is essentially the change you suggested with all of i's dotted
  and the t's crossed so that ptrace can intercept all of the cases it
  has been able to intercept the past, and all of the cases that made it
  to exit without giving ptrace a chance still don't give ptrace a
  chance"

* 'SA_IMMUTABLE-fixes-for-v5.16-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  signal: Replace force_fatal_sig with force_exit_sig when in doubt
  signal: Don't always set SA_IMMUTABLE for forced signals
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Recently to prevent issues with SECCOMP_RET_KILL and similar signals
being changed before they are delivered SA_IMMUTABLE was added.

Unfortunately this broke debuggers[1][2] which reasonably expect
to be able to trap synchronous SIGTRAP and SIGSEGV even when
the target process is not configured to handle those signals.

Add force_exit_sig and use it instead of force_fatal_sig where
historically the code has directly called do_exit.  This has the
implementation benefits of going through the signal exit path
(including generating core dumps) without the danger of allowing
userspace to ignore or change these signals.

This avoids userspace regressions as older kernels exited with do_exit
which debuggers also can not intercept.

In the future is should be possible to improve the quality of
implementation of the kernel by changing some of these force_exit_sig
calls to force_fatal_sig.  That can be done where it matters on
a case-by-case basis with careful analysis.
Reported-by: NKyle Huey <me@kylehuey.com>
Reported-by: Nkernel test robot <oliver.sang@intel.com>
[1] https://lkml.kernel.org/r/CAP045AoMY4xf8aC_4QU_-j7obuEPYgTcnQQP3Yxk=2X90jtpjw@mail.gmail.com
[2] https://lkml.kernel.org/r/20211117150258.GB5403@xsang-OptiPlex-9020
Fixes: 00b06da2 ("signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed")
Fixes: a3616a3c ("signal/m68k: Use force_sigsegv(SIGSEGV) in fpsp040_die")
Fixes: 83a1f27a ("signal/powerpc: On swapcontext failure force SIGSEGV")
Fixes: 9bc508cf ("signal/s390: Use force_sigsegv in default_trap_handler")
Fixes: 086ec444 ("signal/sparc32: In setup_rt_frame and setup_fram use force_fatal_sig")
Fixes: c317d306 ("signal/sparc32: Exit with a fatal signal when try_to_clear_window_buffer fails")
Fixes: 695dd0d6 ("signal/x86: In emulate_vsyscall force a signal instead of calling do_exit")
Fixes: 1fbd60df ("signal/vm86_32: Properly send SIGSEGV when the vm86 state cannot be saved.")
Fixes: 941edc5b ("exit/syscall_user_dispatch: Send ordinary signals on failure")
Link: https://lkml.kernel.org/r/871r3dqfv8.fsf_-_@email.froward.int.ebiederm.orgReviewed-by: NKees Cook <keescook@chromium.org>
Tested-by: NKees Cook <keescook@chromium.org>
Tested-by: NKyle Huey <khuey@kylehuey.com>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Recently to prevent issues with SECCOMP_RET_KILL and similar signals
being changed before they are delivered SA_IMMUTABLE was added.

Unfortunately this broke debuggers[1][2] which reasonably expect to be
able to trap synchronous SIGTRAP and SIGSEGV even when the target
process is not configured to handle those signals.

Update force_sig_to_task to support both the case when we can allow
the debugger to intercept and possibly ignore the signal and the case
when it is not safe to let userspace know about the signal until the
process has exited.
Suggested-by: NLinus Torvalds <torvalds@linux-foundation.org>
Reported-by: NKyle Huey <me@kylehuey.com>
Reported-by: Nkernel test robot <oliver.sang@intel.com>
Cc: stable@vger.kernel.org
[1] https://lkml.kernel.org/r/CAP045AoMY4xf8aC_4QU_-j7obuEPYgTcnQQP3Yxk=2X90jtpjw@mail.gmail.com
[2] https://lkml.kernel.org/r/20211117150258.GB5403@xsang-OptiPlex-9020
Fixes: 00b06da2 ("signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed")
Link: https://lkml.kernel.org/r/877dd5qfw5.fsf_-_@email.froward.int.ebiederm.orgReviewed-by: NKees Cook <keescook@chromium.org>
Tested-by: NKees Cook <keescook@chromium.org>
Tested-by: NKyle Huey <khuey@kylehuey.com>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Kyle Huey recently reported[1] that rr gets confused if SIGKILL prevents
ptrace_signal from delivering a signal, as the kernel setups up a signal
frame for a signal that rr did not have a chance to observe with ptrace.

In looking into it I found a couple of bugs and a quality of
implementation issue.

- The test for signal_group_exit should be inside the for loop in get_signal.
- Signals should be requeued on the same queue they were dequeued from.
- When a fatal signal is pending ptrace_signal should not return another
  signal for delivery.

Kyle Huey has verified[2] an earlier version of this change.

I have reworked things one more time to completely fix the issues
raised, and to keep the code maintainable long term.

I have smoke tested this code and combined with a careful review I
expect this code to work fine.  Kyle if you can double check that
my last round of changes still works for rr I would appreciate it.

Eric W. Biederman (3):
      signal: In get_signal test for signal_group_exit every time through the loop
      signal: Requeue signals in the appropriate queue
      signal: Requeue ptrace signals

 fs/signalfd.c                |  5 +++--
 include/linux/sched/signal.h |  7 ++++---
 kernel/signal.c              | 44 ++++++++++++++++++++++++++------------------
 3 files changed, 33 insertions(+), 23 deletions(-)

[1] https://lkml.kernel.org/r/20211101034147.6203-1-khuey@kylehuey.com
[2] https://lkml.kernel.org/r/CAP045ApAX725ZfujaK-jJNkfCo5s+oVFpBvNfPJk+DKY8K7d=Q@mail.gmail.comTested-by: NKyle Huey <khuey@kylehuey.com>
Link: https://lkml.kernel.org/r/87bl2kekig.fsf_-_@email.froward.int.ebiederm.orgSigned-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Kyle Huey <me@kylehuey.com> writes:

> rr, a userspace record and replay debugger[0], uses the recorded register
> state at PTRACE_EVENT_EXIT to find the point in time at which to cease
> executing the program during replay.
>
> If a SIGKILL races with processing another signal in get_signal, it is
> possible for the kernel to decline to notify the tracer of the original
> signal. But if the original signal had a handler, the kernel proceeds
> with setting up a signal handler frame as if the tracer had chosen to
> deliver the signal unmodified to the tracee. When the kernel goes to
> execute the signal handler that it has now modified the stack and registers
> for, it will discover the pending SIGKILL, and terminate the tracee
> without executing the handler. When PTRACE_EVENT_EXIT is delivered to
> the tracer, however, the effects of handler setup will be visible to
> the tracer.
>
> Because rr (the tracer) was never notified of the signal, it is not aware
> that a signal handler frame was set up and expects the state of the program
> at PTRACE_EVENT_EXIT to be a state that will be reconstructed naturally
> by allowing the program to execute from the last event. When that fails
> to happen during replay, rr will assert and die.
>
> The following patches add an explicit check for a newly pending SIGKILL
> after the ptracer has been notified and the siglock has been reacquired.
> If this happens, we stop processing the current signal and proceed
> immediately to handling the SIGKILL. This makes the state reported at
> PTRACE_EVENT_EXIT the unmodified state of the program, and also avoids the
> work to set up a signal handler frame that will never be used.
>
> [0] https://rr-project.org/

The problem is that while the traced process makes it into ptrace_stop,
the tracee is killed before the tracer manages to wait for the
tracee and discover which signal was about to be delivered.

More generally the problem is that while siglock was dropped a signal
with process wide effect is short cirucit delivered to the entire
process killing it, but the process continues to try and deliver another
signal.

In general it impossible to avoid all cases where work is performed
after the process has been killed.  In particular if the process is
killed after get_signal returns the code will simply not know it has
been killed until after delivering the signal frame to userspace.

On the other hand when the code has already discovered the process
has been killed and taken user space visible action that shows
the kernel knows the process has been killed, it is just silly
to then write the signal frame to the user space stack.

Instead of being silly detect the process has been killed
in ptrace_signal and requeue the signal so the code can pretend
it was simply never dequeued for delivery.

To test the process has been killed I use fatal_signal_pending rather
than signal_group_exit to match the test in signal_pending_state which
is used in schedule which is where ptrace_stop detects the process has
been killed.

Requeuing the signal so the code can pretend it was simply never
dequeued improves the user space visible behavior that has been
present since ebf5ebe31d2c ("[PATCH] signal-fixes-2.5.59-A4").

Kyle Huey verified that this change in behavior and makes rr happy.
Reported-by: NKyle Huey <khuey@kylehuey.com>
Reported-by: NMarko Mäkelä <marko.makela@mariadb.com>
History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.giReviewed-by: NKees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/87tugcd5p2.fsf_-_@email.froward.int.ebiederm.orgSigned-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

In the event that a tracer changes which signal needs to be delivered
and that signal is currently blocked then the signal needs to be
requeued for later delivery.

With the advent of CLONE_THREAD the kernel has 2 signal queues per
task.  The per process queue and the per task queue.  Update the code
so that if the signal is removed from the per process queue it is
requeued on the per process queue.  This is necessary to make it
appear the signal was never dequeued.

The rr debugger reasonably believes that the state of the process from
the last ptrace_stop it observed until PTRACE_EVENT_EXIT can be recreated
by simply letting a process run.  If a SIGKILL interrupts a ptrace_stop
this is not true today.

So return signals to their original queue in ptrace_signal so that
signals that are not delivered appear like they were never dequeued.

Fixes: 794aa320b79d ("[PATCH] sigfix-2.5.40-D6")
History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.giReviewed-by: NKees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/87zgq4d5r4.fsf_-_@email.froward.int.ebiederm.orgSigned-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Recently while investigating a problem with rr and signals I noticed
that siglock is dropped in ptrace_signal and get_signal does not jump
to relock.

Looking farther to see if the problem is anywhere else I see that
do_signal_stop also returns if signal_group_exit is true.  I believe
that test can now never be true, but it is a bit hard to trace
through and be certain.

Testing signal_group_exit is not expensive, so move the test for
signal_group_exit into the for loop inside of get_signal to ensure
the test is never skipped improperly.

This has been a potential problem since I added the test for
signal_group_exit was added.

Fixes: 35634ffa ("signal: Always notice exiting tasks")
Reviewed-by: NKees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/875yssekcd.fsf_-_@email.froward.int.ebiederm.orgSigned-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Add Kconfig support for -Wimplicit-fallthrough for both GCC and Clang.

The compiler option is under configuration CC_IMPLICIT_FALLTHROUGH,
which is enabled by default.

Special thanks to Nathan Chancellor who fixed the Clang bug[1][2]. This
bugfix only appears in Clang 14.0.0, so older versions still contain
the bug and -Wimplicit-fallthrough won't be enabled for them, for now.

This concludes a long journey and now we are finally getting rid
of the unintentional fallthrough bug-class in the kernel, entirely. :)

Link: https://github.com/llvm/llvm-project/commit/9ed4a94d6451046a51ef393cd62f00710820a7e8 [1]
Link: https://bugs.llvm.org/show_bug.cgi?id=51094 [2]
Link: https://github.com/KSPP/linux/issues/115
Link: https://github.com/ClangBuiltLinux/linux/issues/236Co-developed-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NKees Cook <keescook@chromium.org>
Co-developed-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NGustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: NNathan Chancellor <nathan@kernel.org>
Tested-by: NNathan Chancellor <nathan@kernel.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Pull xfs cleanups from Darrick Wong:
 "The most 'exciting' aspect of this branch is that the xfsprogs
  maintainer and I have worked through the last of the code
  discrepancies between kernel and userspace libxfs such that there are
  no code differences between the two except for #includes.

  IOWs, diff suffices to demonstrate that the userspace tools behave the
  same as the kernel, and kernel-only bits are clearly marked in the
  /kernel/ source code instead of just the userspace source.

  Summary:

   - Clean up open-coded swap() calls.

   - A little bit of #ifdef golf to complete the reunification of the
     kernel and userspace libxfs source code"

* tag 'xfs-5.16-merge-5' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  xfs: sync xfs_btree_split macros with userspace libxfs
  xfs: #ifdef out perag code for userspace
  xfs: use swap() to make dabtree code cleaner

Pull more parisc fixes from Helge Deller:
 "Fix a build error in stracktrace.c, fix resolving of addresses to
  function names in backtraces, fix single-stepping in assembly code and
  flush userspace pte's when using set_pte_at()"

* tag 'for-5.16/parisc-3' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  parisc/entry: fix trace test in syscall exit path
  parisc: Flush kernel data mapping in set_pte_at() when installing pte for user page
  parisc: Fix implicit declaration of function '__kernel_text_address'
  parisc: Fix backtrace to always include init funtion names

Pull arch/sh updates from Rich Felker.

* tag 'sh-for-5.16' of git://git.libc.org/linux-sh:
  sh: pgtable-3level: Fix cast to pointer from integer of different size
  sh: fix READ/WRITE redefinition warnings
  sh: define __BIG_ENDIAN for math-emu
  sh: math-emu: drop unused functions
  sh: fix kconfig unmet dependency warning for FRAME_POINTER
  sh: Cleanup about SPARSE_IRQ
  sh: kdump: add some attribute to function
  maple: fix wrong return value of maple_bus_init().
  sh: boot: avoid unneeded rebuilds under arch/sh/boot/compressed/
  sh: boot: add intermediate vmlinux.bin* to targets instead of extra-y
  sh: boards: Fix the cacography in irq.c
  sh: check return code of request_irq
  sh: fix trivial misannotations

Pull ARM fixes from Russell King:

 - Fix early_iounmap

 - Drop cc-option fallbacks for architecture selection

* tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm:
  ARM: 9156/1: drop cc-option fallbacks for architecture selection
  ARM: 9155/1: fix early early_iounmap()

Pull devicetree fixes from Rob Herring:

 - Two fixes due to DT node name changes on Arm, Ltd. boards

 - Treewide rename of Ingenic CGU headers

 - Update ST email addresses

 - Remove Netlogic DT bindings

 - Dropping few more cases of redundant 'maxItems' in schemas

 - Convert toshiba,tc358767 bridge binding to schema

* tag 'devicetree-fixes-for-5.16-1' of git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux:
  dt-bindings: watchdog: sunxi: fix error in schema
  bindings: media: venus: Drop redundant maxItems for power-domain-names
  dt-bindings: Remove Netlogic bindings
  clk: versatile: clk-icst: Ensure clock names are unique
  of: Support using 'mask' in making device bus id
  dt-bindings: treewide: Update @st.com email address to @foss.st.com
  dt-bindings: media: Update maintainers for st,stm32-hwspinlock.yaml
  dt-bindings: media: Update maintainers for st,stm32-cec.yaml
  dt-bindings: mfd: timers: Update maintainers for st,stm32-timers
  dt-bindings: timer: Update maintainers for st,stm32-timer
  dt-bindings: i2c: imx: hardware do not restrict clock-frequency to only 100 and 400 kHz
  dt-bindings: display: bridge: Convert toshiba,tc358767.txt to yaml
  dt-bindings: Rename Ingenic CGU headers to ingenic,*.h

Pull timer fix from Thomas Gleixner:
 "A single fix for POSIX CPU timers to address a problem where POSIX CPU
  timer delivery stops working for a new child task because
  copy_process() copies state information which is only valid for the
  parent task"

* tag 'timers-urgent-2021-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  posix-cpu-timers: Clear task::posix_cputimers_work in copy_process()

Pull irq fixes from Thomas Gleixner:
 "A set of fixes for the interrupt subsystem

  Core code:

   - A regression fix for the Open Firmware interrupt mapping code where
     a interrupt controller property in a node caused a map property in
     the same node to be ignored.

  Interrupt chip drivers:

   - Workaround a limitation in SiFive PLIC interrupt chip which
     silently ignores an EOI when the interrupt line is masked.

   - Provide the missing mask/unmask implementation for the CSKY MP
     interrupt controller.

  PCI/MSI:

   - Prevent a use after free when PCI/MSI interrupts are released by
     destroying the sysfs entries before freeing the memory which is
     accessed in the sysfs show() function.

   - Implement a mask quirk for the Nvidia ION AHCI chip which does not
     advertise masking capability despite implementing it. Even worse
     the chip comes out of reset with all MSI entries masked, which due
     to the missing masking capability never get unmasked.

   - Move the check which prevents accessing the MSI[X] masking for XEN
     back into the low level accessors. The recent consolidation missed
     that these accessors can be invoked from places which do not have
     that check which broke XEN. Move them back to he original place
     instead of sprinkling tons of these checks all over the code"

* tag 'irq-urgent-2021-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  of/irq: Don't ignore interrupt-controller when interrupt-map failed
  irqchip/sifive-plic: Fixup EOI failed when masked
  irqchip/csky-mpintc: Fixup mask/unmask implementation
  PCI/MSI: Destroy sysfs before freeing entries
  PCI: Add MSI masking quirk for Nvidia ION AHCI
  PCI/MSI: Deal with devices lying about their MSI mask capability
  PCI/MSI: Move non-mask check back into low level accessors

Pull x86 static call update from Thomas Gleixner:
 "A single fix for static calls to make the trampoline patching more
  robust by placing explicit signature bytes after the call trampoline
  to prevent patching random other jumps like the CFI jump table
  entries"

* tag 'locking-urgent-2021-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  static_call,x86: Robustify trampoline patching

Pull scheduler fixes from Borislav Petkov:

 - Avoid touching ~100 config files in order to be able to select the
   preemption model

 - clear cluster CPU masks too, on the CPU unplug path

 - prevent use-after-free in cfs

 - Prevent a race condition when updating CPU cache domains

 - Factor out common shared part of smp_prepare_cpus() into a common
   helper which can be called by both baremetal and Xen, in order to fix
   a booting of Xen PV guests

* tag 'sched_urgent_for_v5.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  preempt: Restore preemption model selection configs
  arch_topology: Fix missing clear cluster_cpumask in remove_cpu_topology()
  sched/fair: Prevent dead task groups from regaining cfs_rq's
  sched/core: Mitigate race cpus_share_cache()/update_top_cache_domain()
  x86/smp: Factor out parts of native_smp_prepare_cpus()

Pull perf fixes from Borislav Petkov:

 - Prevent unintentional page sharing by checking whether a page
   reference to a PMU samples page has been acquired properly before
   that

 - Make sure the LBR_SELECT MSR is saved/restored too

 - Reset the LBR_SELECT MSR when resetting the LBR PMU to clear any
   residual data left

* tag 'perf_urgent_for_v5.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/core: Avoid put_page() when GUP fails
  perf/x86/vlbr: Add c->flags to vlbr event constraints
  perf/x86/lbr: Reset LBR_SELECT during vlbr reset

Pull x86 fixes from Borislav Petkov:

 - Add the model number of a new, Raptor Lake CPU, to intel-family.h

 - Do not log spurious corrected MCEs on SKL too, due to an erratum

 - Clarify the path of paravirt ops patches upstream

 - Add an optimization to avoid writing out AMX components to sigframes
   when former are in init state

* tag 'x86_urgent_for_v5.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/cpu: Add Raptor Lake to Intel family
  x86/mce: Add errata workaround for Skylake SKX37
  MAINTAINERS: Add some information to PARAVIRT_OPS entry
  x86/fpu: Optimize out sigframe xfeatures when in init state

Merge tag 'perf-tools-for-v5.16-2021-11-13' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux

Pull more perf tools updates from Arnaldo Carvalho de Melo:
 "Hardware tracing:

   - ARM:
      * Print the size of the buffer size consistently in hexadecimal in
        ARM Coresight.
      * Add Coresight snapshot mode support.
      * Update --switch-events docs in 'perf record'.
      * Support hardware-based PID tracing.
      * Track task context switch for cpu-mode events.

   - Vendor events:
      * Add metric events JSON file for power10 platform

  perf test:

   - Get 'perf test' unit tests closer to kunit.

   - Topology tests improvements.

   - Remove bashisms from some tests.

  perf bench:

   - Fix memory leak of perf_cpu_map__new() in the futex benchmarks.

  libbpf:

   - Add some more weak libbpf functions o allow building with the
     libbpf versions, old ones, present in distros.

  libbeauty:

   - Translate [gs]setsockopt 'level' argument integer values to
     strings.

  tools headers UAPI:

   - Sync futex_waitv, arch prctl, sound, i195_drm and msr-index files
     with the kernel sources.

  Documentation:

   - Add documentation to 'struct symbol'.

   - Synchronize the definition of enum perf_hw_id with code in
     tools/perf/design.txt"

* tag 'perf-tools-for-v5.16-2021-11-13' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux: (67 commits)
  perf tests: Remove bash constructs from stat_all_pmu.sh
  perf tests: Remove bash construct from record+zstd_comp_decomp.sh
  perf test: Remove bash construct from stat_bpf_counters.sh test
  perf bench futex: Fix memory leak of perf_cpu_map__new()
  tools arch x86: Sync the msr-index.h copy with the kernel sources
  tools headers UAPI: Sync drm/i915_drm.h with the kernel sources
  tools headers UAPI: Sync sound/asound.h with the kernel sources
  tools headers UAPI: Sync linux/prctl.h with the kernel sources
  tools headers UAPI: Sync arch prctl headers with the kernel sources
  perf tools: Add more weak libbpf functions
  perf bpf: Avoid memory leak from perf_env__insert_btf()
  perf symbols: Factor out annotation init/exit
  perf symbols: Bit pack to save a byte
  perf symbols: Add documentation to 'struct symbol'
  tools headers UAPI: Sync files changed by new futex_waitv syscall
  perf test bpf: Use ARRAY_CHECK() instead of ad-hoc equivalent, addressing array_size.cocci warning
  perf arm-spe: Support hardware-based PID tracing
  perf arm-spe: Save context ID in record
  perf arm-spe: Update --switch-events docs in 'perf record'
  perf arm-spe: Track task context switch for cpu-mode events
  ...

Merge tag 'irqchip-fixes-5.16-1' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/urgent

Pull irqchip fixes from Marc Zyngier:

  - Address an issue with the SiFive PLIC being unable to EOI
    a masked interrupt

  - Move the disable/enable methods in the CSky mpintc to
    mask/unmask

  - Fix a regression in the OF irq code where an interrupt-controller
    property in the same node as an interrupt-map property would get
    ignored

Link: https://lore.kernel.org/all/20211112173459.4015233-1-maz@kernel.org

Pull zstd update from Nick Terrell:
 "Update to zstd-1.4.10.

  Add myself as the maintainer of zstd and update the zstd version in
  the kernel, which is now 4 years out of date, to a much more recent
  zstd release. This includes bug fixes, much more extensive fuzzing,
  and performance improvements. And generates the kernel zstd
  automatically from upstream zstd, so it is easier to keep the zstd
  verison up to date, and we don't fall so far out of date again.

  This includes 5 commits that update the zstd library version:

   - Adds a new kernel-style wrapper around zstd.

     This wrapper API is functionally equivalent to the subset of the
     current zstd API that is currently used. The wrapper API changes to
     be kernel style so that the symbols don't collide with zstd's
     symbols. The update to zstd-1.4.10 maintains the same API and
     preserves the semantics, so that none of the callers need to be
     updated. All callers are updated in the commit, because there are
     zero functional changes.

   - Adds an indirection for `lib/decompress_unzstd.c` so it doesn't
     depend on the layout of `lib/zstd/` to include every source file.
     This allows the next patch to be automatically generated.

   - Imports the zstd-1.4.10 source code. This commit is automatically
     generated from upstream zstd (https://github.com/facebook/zstd).

   - Adds me (terrelln@fb.com) as the maintainer of `lib/zstd`.

   - Fixes a newly added build warning for clang.

  The discussion around this patchset has been pretty long, so I've
  included a FAQ-style summary of the history of the patchset, and why
  we are taking this approach.

  Why do we need to update?
  -------------------------

  The zstd version in the kernel is based off of zstd-1.3.1, which is
  was released August 20, 2017. Since then zstd has seen many bug fixes
  and performance improvements. And, importantly, upstream zstd is
  continuously fuzzed by OSS-Fuzz, and bug fixes aren't backported to
  older versions. So the only way to sanely get these fixes is to keep
  up to date with upstream zstd.

  There are no known security issues that affect the kernel, but we need
  to be able to update in case there are. And while there are no known
  security issues, there are relevant bug fixes. For example the problem
  with large kernel decompression has been fixed upstream for over 2
  years [1]

  Additionally the performance improvements for kernel use cases are
  significant. Measured for x86_64 on my Intel i9-9900k @ 3.6 GHz:

   - BtrFS zstd compression at levels 1 and 3 is 5% faster

   - BtrFS zstd decompression+read is 15% faster

   - SquashFS zstd decompression+read is 15% faster

   - F2FS zstd compression+write at level 3 is 8% faster

   - F2FS zstd decompression+read is 20% faster

   - ZRAM decompression+read is 30% faster

   - Kernel zstd decompression is 35% faster

   - Initramfs zstd decompression+build is 5% faster

  On top of this, there are significant performance improvements coming
  down the line in the next zstd release, and the new automated update
  patch generation will allow us to pull them easily.

  How is the update patch generated?
  ----------------------------------

  The first two patches are preparation for updating the zstd version.
  Then the 3rd patch in the series imports upstream zstd into the
  kernel. This patch is automatically generated from upstream. A script
  makes the necessary changes and imports it into the kernel. The
  changes are:

   - Replace all libc dependencies with kernel replacements and rewrite
     includes.

   - Remove unncessary portability macros like: #if defined(_MSC_VER).

   - Use the kernel xxhash instead of bundling it.

  This automation gets tested every commit by upstream's continuous
  integration. When we cut a new zstd release, we will submit a patch to
  the kernel to update the zstd version in the kernel.

  The automated process makes it easy to keep the kernel version of zstd
  up to date. The current zstd in the kernel shares the guts of the
  code, but has a lot of API and minor changes to work in the kernel.
  This is because at the time upstream zstd was not ready to be used in
  the kernel envrionment as-is. But, since then upstream zstd has
  evolved to support being used in the kernel as-is.

  Why are we updating in one big patch?
  -------------------------------------

  The 3rd patch in the series is very large. This is because it is
  restructuring the code, so it both deletes the existing zstd, and
  re-adds the new structure. Future updates will be directly
  proportional to the changes in upstream zstd since the last import.
  They will admittidly be large, as zstd is an actively developed
  project, and has hundreds of commits between every release. However,
  there is no other great alternative.

  One option ruled out is to replay every upstream zstd commit. This is
  not feasible for several reasons:

   - There are over 3500 upstream commits since the zstd version in the
     kernel.

   - The automation to automatically generate the kernel update was only
     added recently, so older commits cannot easily be imported.

   - Not every upstream zstd commit builds.

   - Only zstd releases are "supported", and individual commits may have
     bugs that were fixed before a release.

  Another option to reduce the patch size would be to first reorganize
  to the new file structure, and then apply the patch. However, the
  current kernel zstd is formatted with clang-format to be more
  "kernel-like". But, the new method imports zstd as-is, without
  additional formatting, to allow for closer correlation with upstream,
  and easier debugging. So the patch wouldn't be any smaller.

  It also doesn't make sense to import upstream zstd commit by commit
  going forward. Upstream zstd doesn't support production use cases
  running of the development branch. We have a lot of post-commit
  fuzzing that catches many bugs, so indiviudal commits may be buggy,
  but fixed before a release. So going forward, I intend to import every
  (important) zstd release into the Kernel.

  So, while it isn't ideal, updating in one big patch is the only patch
  I see forward.

  Who is responsible for this code?
  ---------------------------------

  I am. This patchset adds me as the maintainer for zstd. Previously,
  there was no tree for zstd patches. Because of that, there were
  several patches that either got ignored, or took a long time to merge,
  since it wasn't clear which tree should pick them up. I'm officially
  stepping up as maintainer, and setting up my tree as the path through
  which zstd patches get merged. I'll make sure that patches to the
  kernel zstd get ported upstream, so they aren't erased when the next
  version update happens.

  How is this code tested?
  ------------------------

  I tested every caller of zstd on x86_64 (BtrFS, ZRAM, SquashFS, F2FS,
  Kernel, InitRAMFS). I also tested Kernel & InitRAMFS on i386 and
  aarch64. I checked both performance and correctness.

  Also, thanks to many people in the community who have tested these
  patches locally.

  Lastly, this code will bake in linux-next before being merged into
  v5.16.

  Why update to zstd-1.4.10 when zstd-1.5.0 has been released?
  ------------------------------------------------------------

  This patchset has been outstanding since 2020, and zstd-1.4.10 was the
  latest release when it was created. Since the update patch is
  automatically generated from upstream, I could generate it from
  zstd-1.5.0.

  However, there were some large stack usage regressions in zstd-1.5.0,
  and are only fixed in the latest development branch. And the latest
  development branch contains some new code that needs to bake in the
  fuzzer before I would feel comfortable releasing to the kernel.

  Once this patchset has been merged, and we've released zstd-1.5.1, we
  can update the kernel to zstd-1.5.1, and exercise the update process.

  You may notice that zstd-1.4.10 doesn't exist upstream. This release
  is an artifical release based off of zstd-1.4.9, with some fixes for
  the kernel backported from the development branch. I will tag the
  zstd-1.4.10 release after this patchset is merged, so the Linux Kernel
  is running a known version of zstd that can be debugged upstream.

  Why was a wrapper API added?
  ----------------------------

  The first versions of this patchset migrated the kernel to the
  upstream zstd API. It first added a shim API that supported the new
  upstream API with the old code, then updated callers to use the new
  shim API, then transitioned to the new code and deleted the shim API.
  However, Cristoph Hellwig suggested that we transition to a kernel
  style API, and hide zstd's upstream API behind that. This is because
  zstd's upstream API is supports many other use cases, and does not
  follow the kernel style guide, while the kernel API is focused on the
  kernel's use cases, and follows the kernel style guide.

  Where is the previous discussion?
  ---------------------------------

  Links for the discussions of the previous versions of the patch set
  below. The largest changes in the design of the patchset are driven by
  the discussions in v11, v5, and v1. Sorry for the mix of links, I
  couldn't find most of the the threads on lkml.org"

Link: https://lkml.org/lkml/2020/9/29/27 [1]
Link: https://www.spinics.net/lists/linux-crypto/msg58189.html [v12]
Link: https://lore.kernel.org/linux-btrfs/20210430013157.747152-1-nickrterrell@gmail.com/ [v11]
Link: https://lore.kernel.org/lkml/20210426234621.870684-2-nickrterrell@gmail.com/ [v10]
Link: https://lore.kernel.org/linux-btrfs/20210330225112.496213-1-nickrterrell@gmail.com/ [v9]
Link: https://lore.kernel.org/linux-f2fs-devel/20210326191859.1542272-1-nickrterrell@gmail.com/ [v8]
Link: https://lkml.org/lkml/2020/12/3/1195 [v7]
Link: https://lkml.org/lkml/2020/12/2/1245 [v6]
Link: https://lore.kernel.org/linux-btrfs/20200916034307.2092020-1-nickrterrell@gmail.com/ [v5]
Link: https://www.spinics.net/lists/linux-btrfs/msg105783.html [v4]
Link: https://lkml.org/lkml/2020/9/23/1074 [v3]
Link: https://www.spinics.net/lists/linux-btrfs/msg105505.html [v2]
Link: https://lore.kernel.org/linux-btrfs/20200916034307.2092020-1-nickrterrell@gmail.com/ [v1]
Signed-off-by: NNick Terrell <terrelln@fb.com>
Tested By: Paul Jones <paul@pauljones.id.au>
Tested-by: NOleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM/Clang v13.0.0 on x86-64
Tested-by: NJean-Denis Girard <jd.girard@sysnux.pf>

* tag 'zstd-for-linus-v5.16' of git://github.com/terrelln/linux:
  lib: zstd: Add cast to silence clang's -Wbitwise-instead-of-logical
  MAINTAINERS: Add maintainer entry for zstd
  lib: zstd: Upgrade to latest upstream zstd version 1.4.10
  lib: zstd: Add decompress_sources.h for decompress_unzstd
  lib: zstd: Add kernel-specific API