linux-stable.git/kernel, branch v4.9.321

kexec_file: drop weak attribute from arch_kexec_apply_relocations[_add]

2022-07-02T14:17:16+00:00

commit 3e35142ef99fe6b4fe5d834ad43ee13cca10a2dc upstream.

Since commit d1bcae833b32f1 ("ELF: Don't generate unused section
symbols") [1], binutils (v2.36+) started dropping section symbols that
it thought were unused.  This isn't an issue in general, but with
kexec_file.c, gcc is placing kexec_arch_apply_relocations[_add] into a
separate .text.unlikely section and the section symbol ".text.unlikely"
is being dropped. Due to this, recordmcount is unable to find a non-weak
symbol in .text.unlikely to generate a relocation record against.

Address this by dropping the weak attribute from these functions.
Instead, follow the existing pattern of having architectures #define the
name of the function they want to override in their headers.

[1] https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d1bcae833b32f1

[akpm@linux-foundation.org: arch/s390/include/asm/kexec.h needs linux/module.h]
Link: https://lkml.kernel.org/r/20220519091237.676736-1-naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Michael Ellerman 
Signed-off-by: Naveen N. Rao 
Cc: "Eric W. Biederman" 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

timekeeping: Add raw clock fallback for random_get_entropy()

2022-06-25T09:45:13+00:00

commit 1366992e16bddd5e2d9a561687f367f9f802e2e4 upstream.

The addition of random_get_entropy_fallback() provides access to
whichever time source has the highest frequency, which is useful for
gathering entropy on platforms without available cycle counters. It's
not necessarily as good as being able to quickly access a cycle counter
that the CPU has, but it's still something, even when it falls back to
being jiffies-based.

In the event that a given arch does not define get_cycles(), falling
back to the get_cycles() default implementation that returns 0 is really
not the best we can do. Instead, at least calling
random_get_entropy_fallback() would be preferable, because that always
needs to return _something_, even falling back to jiffies eventually.
It's not as though random_get_entropy_fallback() is super high precision
or guaranteed to be entropic, but basically anything that's not zero all
the time is better than returning zero all the time.

Finally, since random_get_entropy_fallback() is used during extremely
early boot when randomizing freelists in mm_init(), it can be called
before timekeeping has been initialized. In that case there really is
nothing we can do; jiffies hasn't even started ticking yet. So just give
up and return 0.

Suggested-by: Thomas Gleixner 
Signed-off-by: Jason A. Donenfeld 
Reviewed-by: Thomas Gleixner 
Cc: Arnd Bergmann 
Cc: Theodore Ts'o 
Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Greg Kroah-Hartman

random: clear fast pool, crng, and batches in cpuhp bring up

2022-06-25T09:45:10+00:00

commit 3191dd5a1179ef0fad5a050a1702ae98b6251e8f upstream.

For the irq randomness fast pool, rather than having to use expensive
atomics, which were visibly the most expensive thing in the entire irq
handler, simply take care of the extreme edge case of resetting count to
zero in the cpuhp online handler, just after workqueues have been
reenabled. This simplifies the code a bit and lets us use vanilla
variables rather than atomics, and performance should be improved.

As well, very early on when the CPU comes up, while interrupts are still
disabled, we clear out the per-cpu crng and its batches, so that it
always starts with fresh randomness.

Cc: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Theodore Ts'o 
Cc: Sultan Alsawaf 
Cc: Dominik Brodowski 
Acked-by: Sebastian Andrzej Siewior 
Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Greg Kroah-Hartman

workqueue: make workqueue available early during boot

2022-06-25T09:45:09+00:00

commit 3347fa0928210d96aaa2bd6cd5a8391d5e630873 upstream.

Workqueue is currently initialized in an early init call; however,
there are cases where early boot code has to be split and reordered to
come after workqueue initialization or the same code path which makes
use of workqueues is used both before workqueue initailization and
after. The latter cases have to gate workqueue usages with
keventd_up() tests, which is nasty and easy to get wrong.

Workqueue usages have become widespread and it'd be a lot more
convenient if it can be used very early from boot. This patch splits
workqueue initialization into two steps. workqueue_init_early() which
sets up the basic data structures so that workqueues can be created
and work items queued, and workqueue_init() which actually brings up
workqueues online and starts executing queued work items. The former
step can be done very early during boot once memory allocation,
cpumasks and idr are initialized. The latter right after kthreads
become available.

This allows work item queueing and canceling from very early boot
which is what most of these use cases want.

* As systemd_wq being initialized doesn't indicate that workqueue is
fully online anymore, update keventd_up() to test wq_online instead.
The follow-up patches will get rid of all its usages and the
function itself.

* Flushing doesn't make sense before workqueue is fully initialized.
The flush functions trigger WARN and return immediately before fully
online.

* Work items are never in-flight before fully online. Canceling can
always succeed by skipping the flush step.

* Some code paths can no longer assume to be called with irq enabled
as irq is disabled during early boot. Use irqsave/restore
operations instead.

v2: Watchdog init, which requires timer to be running, moved from
workqueue_init_early() to workqueue_init().

Signed-off-by: Tejun Heo
Suggested-by: Linus Torvalds
Link: http://lkml.kernel.org/r/CA+55aFx0vPuMuxn00rBSM192n-Du5uxy+4AvKa0SBSOVJeuCGg@mail.gmail.com
Signed-off-by: Jason A. Donenfeld
Signed-off-by: Greg Kroah-Hartman

random: remove unused irq_flags argument from add_interrupt_randomness()

2022-06-25T09:45:04+00:00

commit 703f7066f40599c290babdb79dd61319264987e9 upstream.

Since commit
   ee3e00e9e7101 ("random: use registers from interrupted code for CPU's w/o a cycle counter")

the irq_flags argument is no longer used.

Remove unused irq_flags.

Cc: Borislav Petkov 
Cc: Dave Hansen 
Cc: Dexuan Cui 
Cc: H. Peter Anvin 
Cc: Haiyang Zhang 
Cc: Ingo Molnar 
Cc: K. Y. Srinivasan 
Cc: Stephen Hemminger 
Cc: Thomas Gleixner 
Cc: Wei Liu 
Cc: linux-hyperv@vger.kernel.org
Cc: x86@kernel.org
Signed-off-by: Sebastian Andrzej Siewior 
Acked-by: Wei Liu 
Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Greg Kroah-Hartman

tracing: Avoid adding tracer option before update_tracer_options

2022-06-14T14:52:38+00:00

[ Upstream commit ef9188bcc6ca1d8a2ad83e826b548e6820721061 ]

To prepare for support asynchronous tracer_init_tracefs initcall,
avoid calling create_trace_option_files before __update_tracer_options.
Otherwise, create_trace_option_files will show warning because
some tracers in trace_types list are already in tr->topts.

For example, hwlat_tracer call register_tracer in late_initcall,
and global_trace.dir is already created in tracing_init_dentry,
hwlat_tracer will be put into tr->topts.
Then if the __update_tracer_options is executed after hwlat_tracer
registered, create_trace_option_files find that hwlat_tracer is
already in tr->topts.

Link: https://lkml.kernel.org/r/20220426122407.17042-2-mark-pk.tsai@mediatek.com

Link: https://lore.kernel.org/lkml/20220322133339.GA32582@xsang-OptiPlex-9020/
Reported-by: kernel test robot 
Signed-off-by: Mark-PK Tsai 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Sasha Levin

ptrace: Reimplement PTRACE_KILL by always sending SIGKILL

2022-06-14T14:52:28+00:00

commit 6a2d90ba027adba528509ffa27097cffd3879257 upstream.

The current implementation of PTRACE_KILL is buggy and has been for
many years as it assumes it's target has stopped in ptrace_stop.  At a
quick skim it looks like this assumption has existed since ptrace
support was added in linux v1.0.

While PTRACE_KILL has been deprecated we can not remove it as
a quick search with google code search reveals many existing
programs calling it.

When the ptracee is not stopped at ptrace_stop some fields would be
set that are ignored except in ptrace_stop.  Making the userspace
visible behavior of PTRACE_KILL a noop in those case.

As the usual rules are not obeyed it is not clear what the
consequences are of calling PTRACE_KILL on a running process.
Presumably userspace does not do this as it achieves nothing.

Replace the implementation of PTRACE_KILL with a simple
send_sig_info(SIGKILL) followed by a return 0.  This changes the
observable user space behavior only in that PTRACE_KILL on a process
not stopped in ptrace_stop will also kill it.  As that has always
been the intent of the code this seems like a reasonable change.

Cc: stable@vger.kernel.org
Reported-by: Al Viro 
Suggested-by: Al Viro 
Tested-by: Kees Cook 
Reviewed-by: Oleg Nesterov 
Link: https://lkml.kernel.org/r/20220505182645.497868-7-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

perf: Fix sys_perf_event_open() race against self

2022-05-25T06:39:49+00:00

commit 3ac6487e584a1eb54071dbe1212e05b884136704 upstream.

Norbert reported that it's possible to race sys_perf_event_open() such
that the looser ends up in another context from the group leader,
triggering many WARNs.

The move_group case checks for races against itself, but the
!move_group case doesn't, seemingly relying on the previous
group_leader->ctx == ctx check. However, that check is racy due to not
holding any locks at that time.

Therefore, re-check the result after acquiring locks and bailing
if they no longer match.

Additionally, clarify the not_move_group case from the
move_group-vs-move_group race.

Fixes: f63a8daa5812 ("perf: Fix event->ctx locking")
Reported-by: Norbert Slusarek 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

smp: Fix offline cpu check in flush_smp_call_function_queue()

2022-04-20T07:06:46+00:00

commit 9e949a3886356fe9112c6f6f34a6e23d1d35407f upstream.

The check in flush_smp_call_function_queue() for callbacks that are sent
to offline CPUs currently checks whether the queue is empty.

However, flush_smp_call_function_queue() has just deleted all the
callbacks from the queue and moved all the entries into a local list.
This checks would only be positive if some callbacks were added in the
short time after llist_del_all() was called. This does not seem to be
the intention of this check.

Change the check to look at the local list to which the entries were
moved instead of the queue from which all the callbacks were just
removed.

Fixes: 8d056c48e4862 ("CPU hotplug, smp: flush any pending IPI callbacks before CPU offline")
Signed-off-by: Nadav Amit 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20220319072015.1495036-1-namit@vmware.com
Signed-off-by: Greg Kroah-Hartman

printk: fix return value of printk.devkmsg __setup handler

2022-04-20T07:06:33+00:00

[ Upstream commit b665eae7a788c5e2bc10f9ac3c0137aa0ad1fc97 ]

If an invalid option value is used with "printk.devkmsg=",
it is silently ignored.
If a valid option value is used, it is honored but the wrong return
value (0) is used, indicating that the command line option had an
error and was not handled. This string is not added to init's
environment strings due to init/main.c::unknown_bootoption()
checking for a '.' in the boot option string and then considering
that string to be an "Unused module parameter".

Print a warning message if a bad option string is used.
Always return 1 from the __setup handler to indicate that the command
line option has been handled.

Fixes: 750afe7babd1 ("printk: add kernel parameter to control writes to /dev/kmsg")
Signed-off-by: Randy Dunlap 
Reported-by: Igor Zhbanov 
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru
Cc: Borislav Petkov 
Cc: Andrew Morton 
Cc: Petr Mladek 
Cc: Sergey Senozhatsky 
Cc: Steven Rostedt 
Cc: John Ogness 
Reviewed-by: John Ogness 
Reviewed-by: Sergey Senozhatsky 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20220228220556.23484-1-rdunlap@infradead.org
Signed-off-by: Sasha Levin