linux.git/kernel, branch v4.4.215

trigger_next should increase position index

2020-02-28T14:39:08+00:00

[ Upstream commit 6722b23e7a2ace078344064a9735fb73e554e9ef ]

if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.

Without patch:
 # dd bs=30 skip=1 if=/sys/kernel/tracing/events/sched/sched_switch/trigger
 dd: /sys/kernel/tracing/events/sched/sched_switch/trigger: cannot skip to specified offset
 n traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
 # Available triggers:
 # traceon traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
 6+1 records in
 6+1 records out
 206 bytes copied, 0.00027916 s, 738 kB/s

Notice the printing of "# Available triggers:..." after the line.

With the patch:
 # dd bs=30 skip=1 if=/sys/kernel/tracing/events/sched/sched_switch/trigger
 dd: /sys/kernel/tracing/events/sched/sched_switch/trigger: cannot skip to specified offset
 n traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
 2+1 records in
 2+1 records out
 88 bytes copied, 0.000526867 s, 167 kB/s

It only prints the end of the file, and does not restart.

Link: http://lkml.kernel.org/r/3c35ee24-dd3a-8119-9c19-552ed253388a@virtuozzo.com

https://bugzilla.kernel.org/show_bug.cgi?id=206283
Signed-off-by: Vasily Averin 
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Sasha Levin

tracing: Fix very unlikely race of registering two stat tracers

2020-02-28T14:38:55+00:00

[ Upstream commit dfb6cd1e654315168e36d947471bd2a0ccd834ae ]

Looking through old emails in my INBOX, I came across a patch from Luis
Henriques that attempted to fix a race of two stat tracers registering the
same stat trace (extremely unlikely, as this is done in the kernel, and
probably doesn't even exist). The submitted patch wasn't quite right as it
needed to deal with clean up a bit better (if two stat tracers were the
same, it would have the same files).

But to make the code cleaner, all we needed to do is to keep the
all_stat_sessions_mutex held for most of the registering function.

Link: http://lkml.kernel.org/r/1410299375-20068-1-git-send-email-luis.henriques@canonical.com

Fixes: 002bb86d8d42f ("tracing/ftrace: separate events tracing and stats tracing engine")
Reported-by: Luis Henriques 
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Sasha Levin

padata: Remove broken queue flushing

2020-02-28T14:38:49+00:00

commit 07928d9bfc81640bab36f5190e8725894d93b659 upstream.

The function padata_flush_queues is fundamentally broken because
it cannot force padata users to complete the request that is
underway.  IOW padata has to passively wait for the completion
of any outstanding work.

As it stands flushing is used in two places.  Its use in padata_stop
is simply unnecessary because nothing depends on the queues to
be flushed afterwards.

The other use in padata_replace is more substantial as we depend
on it to free the old pd structure.  This patch instead uses the
pd->refcnt to dynamically free the pd structure once all requests
are complete.

Fixes: 2b73b07ab8a4 ("padata: Flush the padata queues actively")
Cc: 
Signed-off-by: Herbert Xu 
Reviewed-by: Daniel Jordan 
Signed-off-by: Herbert Xu 
[dj: leave "pd->pinst = pinst" assignment in padata_alloc_pd()]
Signed-off-by: Daniel Jordan 
Signed-off-by: Greg Kroah-Hartman

perf/core: Fix mlock accounting in perf_mmap()

2020-02-14T21:30:01+00:00

commit 003461559ef7a9bd0239bae35a22ad8924d6e9ad upstream.

Decreasing sysctl_perf_event_mlock between two consecutive perf_mmap()s of
a perf ring buffer may lead to an integer underflow in locked memory
accounting. This may lead to the undesired behaviors, such as failures in
BPF map creation.

Address this by adjusting the accounting logic to take into account the
possibility that the amount of already locked memory may exceed the
current limit.

Fixes: c4b75479741c ("perf/core: Make the mlock accounting simple again")
Suggested-by: Alexander Shishkin 
Signed-off-by: Song Liu 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Cc: 
Acked-by: Alexander Shishkin 
Link: https://lkml.kernel.org/r/20200123181146.2238074-1-songliubraving@fb.com
Signed-off-by: Greg Kroah-Hartman

clocksource: Prevent double add_timer_on() for watchdog_timer

2020-02-14T21:30:01+00:00

commit febac332a819f0e764aa4da62757ba21d18c182b upstream.

Kernel crashes inside QEMU/KVM are observed:

  kernel BUG at kernel/time/timer.c:1154!
  BUG_ON(timer_pending(timer) || !timer->function) in add_timer_on().

At the same time another cpu got:

  general protection fault: 0000 [#1] SMP PTI of poinson pointer 0xdead000000000200 in:

  __hlist_del at include/linux/list.h:681
  (inlined by) detach_timer at kernel/time/timer.c:818
  (inlined by) expire_timers at kernel/time/timer.c:1355
  (inlined by) __run_timers at kernel/time/timer.c:1686
  (inlined by) run_timer_softirq at kernel/time/timer.c:1699

Unfortunately kernel logs are badly scrambled, stacktraces are lost.

Printing the timer->function before the BUG_ON() pointed to
clocksource_watchdog().

The execution of clocksource_watchdog() can race with a sequence of
clocksource_stop_watchdog() .. clocksource_start_watchdog():

expire_timers()
 detach_timer(timer, true);
  timer->entry.pprev = NULL;
 raw_spin_unlock_irq(&base->lock);
 call_timer_fn
  clocksource_watchdog()

					clocksource_watchdog_kthread() or
					clocksource_unbind()

					spin_lock_irqsave(&watchdog_lock, flags);
					clocksource_stop_watchdog();
					 del_timer(&watchdog_timer);
					 watchdog_running = 0;
					spin_unlock_irqrestore(&watchdog_lock, flags);

					spin_lock_irqsave(&watchdog_lock, flags);
					clocksource_start_watchdog();
					 add_timer_on(&watchdog_timer, ...);
					 watchdog_running = 1;
					spin_unlock_irqrestore(&watchdog_lock, flags);

  spin_lock(&watchdog_lock);
  add_timer_on(&watchdog_timer, ...);
   BUG_ON(timer_pending(timer) || !timer->function);
    timer_pending() -> true
    BUG()

I.e. inside clocksource_watchdog() watchdog_timer could be already armed.

Check timer_pending() before calling add_timer_on(). This is sufficient as
all operations are synchronized by watchdog_lock.

Fixes: 75c5158f70c0 ("timekeeping: Update clocksource with stop_machine")
Signed-off-by: Konstantin Khlebnikov 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/158048693917.4378.13823603769948933793.stgit@buzz
Signed-off-by: Greg Kroah-Hartman

signal: Allow cifs and drbd to receive their terminating signals

2020-01-29T09:21:47+00:00

[ Upstream commit 33da8e7c814f77310250bb54a9db36a44c5de784 ]

My recent to change to only use force_sig for a synchronous events
wound up breaking signal reception cifs and drbd.  I had overlooked
the fact that by default kthreads start out with all signals set to
SIG_IGN.  So a change I thought was safe turned out to have made it
impossible for those kernel thread to catch their signals.

Reverting the work on force_sig is a bad idea because what the code
was doing was very much a misuse of force_sig.  As the way force_sig
ultimately allowed the signal to happen was to change the signal
handler to SIG_DFL.  Which after the first signal will allow userspace
to send signals to these kernel threads.  At least for
wake_ack_receiver in drbd that does not appear actively wrong.

So correct this problem by adding allow_kernel_signal that will allow
signals whose siginfo reports they were sent by the kernel through,
but will not allow userspace generated signals, and update cifs and
drbd to call allow_kernel_signal in an appropriate place so that their
thread can receive this signal.

Fixing things this way ensures that userspace won't be able to send
signals and cause problems, that it is clear which signals the
threads are expecting to receive, and it guarantees that nothing
else in the system will be affected.

This change was partly inspired by similar cifs and drbd patches that
added allow_signal.

Reported-by: ronnie sahlberg 
Reported-by: Christoph Böhmwalder 
Tested-by: Christoph Böhmwalder 
Cc: Steve French 
Cc: Philipp Reisner 
Cc: David Laight 
Fixes: 247bc9470b1e ("cifs: fix rmmod regression in cifs.ko caused by force_sig changes")
Fixes: 72abe3bcf091 ("signal/cifs: Fix cifs_put_tcp_session to call send_sig instead of force_sig")
Fixes: fee109901f39 ("signal/drbd: Use send_sig not force_sig")
Fixes: 3cf5d076fb4d ("signal: Remove task parameter from force_sig")
Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Sasha Levin

kdb: do a sanity check on the cpu in kdb_per_cpu()

2020-01-29T09:21:43+00:00

[ Upstream commit b586627e10f57ee3aa8f0cfab0d6f7dc4ae63760 ]

The "whichcpu" comes from argv[3].  The cpu_online() macro looks up the
cpu in a bitmap of online cpus, but if the value is too high then it
could read beyond the end of the bitmap and possibly Oops.

Fixes: 5d5314d6795f ("kdb: core for kgdb back end (1 of 2)")
Signed-off-by: Dan Carpenter 
Reviewed-by: Douglas Anderson 
Signed-off-by: Daniel Thompson 
Signed-off-by: Sasha Levin

tracing: Have stack tracer compile when MCOUNT_INSN_SIZE is not defined

2020-01-14T19:03:01+00:00

commit b8299d362d0837ae39e87e9019ebe6b736e0f035 upstream.

On some archs with some configurations, MCOUNT_INSN_SIZE is not defined, and
this makes the stack tracer fail to compile. Just define it to zero in this
case.

Link: https://lore.kernel.org/r/202001020219.zvE3vsty%lkp@intel.com

Cc: stable@vger.kernel.org
Fixes: 4df297129f622 ("tracing: Remove most or all of stack tracer stack size from stack_max_size")
Reported-by: kbuild test robot 
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Greg Kroah-Hartman

kernel/trace: Fix do not unregister tracepoints when register sched_migrate_task fail

2020-01-14T19:03:01+00:00

commit 50f9ad607ea891a9308e67b81f774c71736d1098 upstream.

In the function, if register_trace_sched_migrate_task() returns error,
sched_switch/sched_wakeup_new/sched_wakeup won't unregister. That is
why fail_deprobe_sched_switch was added.

Link: http://lkml.kernel.org/r/20191231133530.2794-1-pilgrimtao@gmail.com

Cc: stable@vger.kernel.org
Fixes: 478142c39c8c2 ("tracing: do not grab lock in wakeup latency function tracing")
Signed-off-by: Kaitao Cheng 
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Greg Kroah-Hartman

locking/spinlock/debug: Fix various data races

2020-01-12T10:22:46+00:00

[ Upstream commit 1a365e822372ba24c9da0822bc583894f6f3d821 ]

This fixes various data races in spinlock_debug. By testing with KCSAN,
it is observable that the console gets spammed with data races reports,
suggesting these are extremely frequent.

Example data race report:

  read to 0xffff8ab24f403c48 of 4 bytes by task 221 on cpu 2:
   debug_spin_lock_before kernel/locking/spinlock_debug.c:85 [inline]
   do_raw_spin_lock+0x9b/0x210 kernel/locking/spinlock_debug.c:112
   __raw_spin_lock include/linux/spinlock_api_smp.h:143 [inline]
   _raw_spin_lock+0x39/0x40 kernel/locking/spinlock.c:151
   spin_lock include/linux/spinlock.h:338 [inline]
   get_partial_node.isra.0.part.0+0x32/0x2f0 mm/slub.c:1873
   get_partial_node mm/slub.c:1870 [inline]
  

  write to 0xffff8ab24f403c48 of 4 bytes by task 167 on cpu 3:
   debug_spin_unlock kernel/locking/spinlock_debug.c:103 [inline]
   do_raw_spin_unlock+0xc9/0x1a0 kernel/locking/spinlock_debug.c:138
   __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:159 [inline]
   _raw_spin_unlock_irqrestore+0x2d/0x50 kernel/locking/spinlock.c:191
   spin_unlock_irqrestore include/linux/spinlock.h:393 [inline]
   free_debug_processing+0x1b3/0x210 mm/slub.c:1214
   __slab_free+0x292/0x400 mm/slub.c:2864
  

As a side-effect, with KCSAN, this eventually locks up the console, most
likely due to deadlock, e.g. .. -> printk lock -> spinlock_debug ->
KCSAN detects data race -> kcsan_print_report() -> printk lock ->
deadlock.

This fix will 1) avoid the data races, and 2) allow using lock debugging
together with KCSAN.

Reported-by: Qian Cai 
Signed-off-by: Marco Elver 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Link: https://lkml.kernel.org/r/20191120155715.28089-1-elver@google.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin