linux-stable.git/kernel, branch v4.9.232

uprobes: Change handle_swbp() to send SIGTRAP with si_code=SI_KERNEL, to fix GDB regression

2020-07-31T14:44:02+00:00

commit fe5ed7ab99c656bd2f5b79b49df0e9ebf2cead8a upstream.

If a tracee is uprobed and it hits int3 inserted by debugger, handle_swbp()
does send_sig(SIGTRAP, current, 0) which means si_code == SI_USER. This used
to work when this code was written, but then GDB started to validate si_code
and now it simply can't use breakpoints if the tracee has an active uprobe:

	# cat test.c
	void unused_func(void)
	{
	}
	int main(void)
	{
		return 0;
	}

	# gcc -g test.c -o test
	# perf probe -x ./test -a unused_func
	# perf record -e probe_test:unused_func gdb ./test -ex run
	GNU gdb (GDB) 10.0.50.20200714-git
	...
	Program received signal SIGTRAP, Trace/breakpoint trap.
	0x00007ffff7ddf909 in dl_main () from /lib64/ld-linux-x86-64.so.2
	(gdb)

The tracee hits the internal breakpoint inserted by GDB to monitor shared
library events but GDB misinterprets this SIGTRAP and reports a signal.

Change handle_swbp() to use force_sig(SIGTRAP), this matches do_int3_user()
and fixes the problem.

This is the minimal fix for -stable, arch/x86/kernel/uprobes.c is equally
wrong; it should use send_sigtrap(TRAP_TRACE) instead of send_sig(SIGTRAP),
but this doesn't confuse GDB and needs another x86-specific patch.

Reported-by: Aaron Merey 
Signed-off-by: Oleg Nesterov 
Signed-off-by: Ingo Molnar 
Reviewed-by: Srikar Dronamraju 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200723154420.GA32043@redhat.com
Signed-off-by: Greg Kroah-Hartman

sched/fair: handle case of task_h_load() returning 0

2020-07-22T07:10:54+00:00

commit 01cfcde9c26d8555f0e6e9aea9d6049f87683998 upstream.

task_h_load() can return 0 in some situations like running stress-ng
mmapfork, which forks thousands of threads, in a sched group on a 224 cores
system. The load balance doesn't handle this correctly because
env->imbalance never decreases and it will stop pulling tasks only after
reaching loop_max, which can be equal to the number of running tasks of
the cfs. Make sure that imbalance will be decreased by at least 1.

misfit task is the other feature that doesn't handle correctly such
situation although it's probably more difficult to face the problem
because of the smaller number of CPUs and running tasks on heterogenous
system.

We can't simply ensure that task_h_load() returns at least one because it
would imply to handle underflow in other places.

Signed-off-by: Vincent Guittot 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Valentin Schneider 
Reviewed-by: Dietmar Eggemann 
Tested-by: Dietmar Eggemann 
Cc:  # v4.4+
Link: https://lkml.kernel.org/r/20200710152426.16981-1-vincent.guittot@linaro.org
Signed-off-by: Greg Kroah-Hartman

timer: Fix wheel index calculation on last level

2020-07-22T07:10:53+00:00

commit e2a71bdea81690b6ef11f4368261ec6f5b6891aa upstream.

When an expiration delta falls into the last level of the wheel, that delta
has be compared against the maximum possible delay and reduced to fit in if
necessary.

However instead of comparing the delta against the maximum, the code
compares the actual expiry against the maximum. Then instead of fixing the
delta to fit in, it sets the maximum delta as the expiry value.

This can result in various undesired outcomes, the worst possible one
being a timer expiring 15 days ahead to fire immediately.

Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel")
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200717140551.29076-2-frederic@kernel.org
Signed-off-by: Greg Kroah-Hartman

cgroup: fix cgroup_sk_alloc() for sk_clone_lock()

2020-07-22T07:10:48+00:00

[ Upstream commit ad0f75e5f57ccbceec13274e1e242f2b5a6397ed ]

When we clone a socket in sk_clone_lock(), its sk_cgrp_data is
copied, so the cgroup refcnt must be taken too. And, unlike the
sk_alloc() path, sock_update_netprioidx() is not called here.
Therefore, it is safe and necessary to grab the cgroup refcnt
even when cgroup_sk_alloc is disabled.

sk_clone_lock() is in BH context anyway, the in_interrupt()
would terminate this function if called there. And for sk_alloc()
skcd->val is always zero. So it's safe to factor out the code
to make it more readable.

The global variable 'cgroup_sk_alloc_disabled' is used to determine
whether to take these reference counts. It is impossible to make
the reference counting correct unless we save this bit of information
in skcd->val. So, add a new bit there to record whether the socket
has already taken the reference counts. This obviously relies on
kmalloc() to align cgroup pointers to at least 4 bytes,
ARCH_KMALLOC_MINALIGN is certainly larger than that.

This bug seems to be introduced since the beginning, commit
d979a39d7242 ("cgroup: duplicate cgroup reference when cloning sockets")
tried to fix it but not compeletely. It seems not easy to trigger until
the recent commit 090e28b229af
("netprio_cgroup: Fix unlimited memory leak of v2 cgroups") was merged.

Fixes: bd1060a1d671 ("sock, cgroup: add sock->sk_cgroup")
Reported-by: Cameron Berkenpas 
Reported-by: Peter Geis 
Reported-by: Lu Fengqi 
Reported-by: Daniël Sonck 
Reported-by: Zhang Qiang 
Tested-by: Cameron Berkenpas 
Tested-by: Peter Geis 
Tested-by: Thomas Lamprecht 
Cc: Daniel Borkmann 
Cc: Zefan Li 
Cc: Tejun Heo 
Cc: Roman Gushchin 
Signed-off-by: Cong Wang 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

sched/rt: Show the 'sched_rr_timeslice' SCHED_RR timeslice tuning knob in milliseconds

2020-07-09T07:35:55+00:00

[ Upstream commit 975e155ed8732cb81f55c021c441ae662dd040b5 ]

We added the 'sched_rr_timeslice_ms' SCHED_RR tuning knob in this commit:

  ce0dbbbb30ae ("sched/rt: Add a tuning knob to allow changing SCHED_RR timeslice")

... which name suggests to users that it's in milliseconds, while in reality
it's being set in milliseconds but the result is shown in jiffies.

This is obviously confusing when HZ is not 1000, it makes it appear like the
value set failed, such as HZ=100:

  root# echo 100 > /proc/sys/kernel/sched_rr_timeslice_ms
  root# cat /proc/sys/kernel/sched_rr_timeslice_ms
  10

Fix this to be milliseconds all around.

Signed-off-by: Shile Zhang 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1485612049-20923-1-git-send-email-shile.zhang@nokia.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

kgdb: Avoid suspicious RCU usage warning

2020-07-09T07:35:55+00:00

[ Upstream commit 440ab9e10e2e6e5fd677473ee6f9e3af0f6904d6 ]

At times when I'm using kgdb I see a splat on my console about
suspicious RCU usage.  I managed to come up with a case that could
reproduce this that looked like this:

  WARNING: suspicious RCU usage
  5.7.0-rc4+ #609 Not tainted
  -----------------------------
  kernel/pid.c:395 find_task_by_pid_ns() needs rcu_read_lock() protection!

  other info that might help us debug this:

    rcu_scheduler_active = 2, debug_locks = 1
  3 locks held by swapper/0/1:
   #0: ffffff81b6b8e988 (&dev->mutex){....}-{3:3}, at: __device_attach+0x40/0x13c
   #1: ffffffd01109e9e8 (dbg_master_lock){....}-{2:2}, at: kgdb_cpu_enter+0x20c/0x7ac
   #2: ffffffd01109ea90 (dbg_slave_lock){....}-{2:2}, at: kgdb_cpu_enter+0x3ec/0x7ac

  stack backtrace:
  CPU: 7 PID: 1 Comm: swapper/0 Not tainted 5.7.0-rc4+ #609
  Hardware name: Google Cheza (rev3+) (DT)
  Call trace:
   dump_backtrace+0x0/0x1b8
   show_stack+0x1c/0x24
   dump_stack+0xd4/0x134
   lockdep_rcu_suspicious+0xf0/0x100
   find_task_by_pid_ns+0x5c/0x80
   getthread+0x8c/0xb0
   gdb_serial_stub+0x9d4/0xd04
   kgdb_cpu_enter+0x284/0x7ac
   kgdb_handle_exception+0x174/0x20c
   kgdb_brk_fn+0x24/0x30
   call_break_hook+0x6c/0x7c
   brk_handler+0x20/0x5c
   do_debug_exception+0x1c8/0x22c
   el1_sync_handler+0x3c/0xe4
   el1_sync+0x7c/0x100
   rpmh_rsc_probe+0x38/0x420
   platform_drv_probe+0x94/0xb4
   really_probe+0x134/0x300
   driver_probe_device+0x68/0x100
   __device_attach_driver+0x90/0xa8
   bus_for_each_drv+0x84/0xcc
   __device_attach+0xb4/0x13c
   device_initial_probe+0x18/0x20
   bus_probe_device+0x38/0x98
   device_add+0x38c/0x420

If I understand properly we should just be able to blanket kgdb under
one big RCU read lock and the problem should go away.  We'll add it to
the beast-of-a-function known as kgdb_cpu_enter().

With this I no longer get any splats and things seem to work fine.

Signed-off-by: Douglas Anderson 
Link: https://lore.kernel.org/r/20200602154729.v2.1.I70e0d4fd46d5ed2aaf0c98a355e8e1b7a5bb7e4e@changeid
Signed-off-by: Daniel Thompson 
Signed-off-by: Sasha Levin

tracing: Fix event trigger to accept redundant spaces

2020-06-30T19:38:45+00:00

commit 6784beada631800f2c5afd567e5628c843362cee upstream.

Fix the event trigger to accept redundant spaces in
the trigger input.

For example, these return -EINVAL

echo " traceon" > events/ftrace/print/trigger
echo "traceon  if common_pid == 0" > events/ftrace/print/trigger
echo "disable_event:kmem:kmalloc " > events/ftrace/print/trigger

But these are hard to find what is wrong.

To fix this issue, use skip_spaces() to remove spaces
in front of actual tokens, and set NULL if there is no
token.

Link: http://lkml.kernel.org/r/159262476352.185015.5261566783045364186.stgit@devnote2

Cc: Tom Zanussi 
Cc: stable@vger.kernel.org
Fixes: 85f2b08268c0 ("tracing: Add basic event trigger framework")
Reviewed-by: Tom Zanussi 
Signed-off-by: Masami Hiramatsu 
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Greg Kroah-Hartman

blktrace: break out of blktrace setup on concurrent calls

2020-06-30T19:38:43+00:00

[ Upstream commit 1b0b283648163dae2a214ca28ed5a99f62a77319 ]

We use one blktrace per request_queue, that means one per the entire
disk.  So we cannot run one blktrace on say /dev/vda and then /dev/vda1,
or just two calls on /dev/vda.

We check for concurrent setup only at the very end of the blktrace setup though.

If we try to run two concurrent blktraces on the same block device the
second one will fail, and the first one seems to go on. However when
one tries to kill the first one one will see things like this:

The kernel will show these:

```
debugfs: File 'dropped' in directory 'nvme1n1' already present!
debugfs: File 'msg' in directory 'nvme1n1' already present!
debugfs: File 'trace0' in directory 'nvme1n1' already present!
``

And userspace just sees this error message for the second call:

```
blktrace /dev/nvme1n1
BLKTRACESETUP(2) /dev/nvme1n1 failed: 5/Input/output error
```

The first userspace process #1 will also claim that the files
were taken underneath their nose as well. The files are taken
away form the first process given that when the second blktrace
fails, it will follow up with a BLKTRACESTOP and BLKTRACETEARDOWN.
This means that even if go-happy process #1 is waiting for blktrace
data, we *have* been asked to take teardown the blktrace.

This can easily be reproduced with break-blktrace [0] run_0005.sh test.

Just break out early if we know we're already going to fail, this will
prevent trying to create the files all over again, which we know still
exist.

[0] https://github.com/mcgrof/break-blktrace

Signed-off-by: Luis Chamberlain 
Signed-off-by: Jan Kara 
Reviewed-by: Bart Van Assche 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

sched/core: Fix PI boosting between RT and DEADLINE tasks

2020-06-30T19:38:43+00:00

[ Upstream commit 740797ce3a124b7dd22b7fb832d87bc8fba1cf6f ]

syzbot reported the following warning:

 WARNING: CPU: 1 PID: 6351 at kernel/sched/deadline.c:628
 enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504

At deadline.c:628 we have:

 623 static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
 624 {
 625 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 626 	struct rq *rq = rq_of_dl_rq(dl_rq);
 627
 628 	WARN_ON(dl_se->dl_boosted);
 629 	WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
        [...]
     }

Which means that setup_new_dl_entity() has been called on a task
currently boosted. This shouldn't happen though, as setup_new_dl_entity()
is only called when the 'dynamic' deadline of the new entity
is in the past w.r.t. rq_clock and boosted tasks shouldn't verify this
condition.

Digging through the PI code I noticed that what above might in fact happen
if an RT tasks blocks on an rt_mutex hold by a DEADLINE task. In the
first branch of boosting conditions we check only if a pi_task 'dynamic'
deadline is earlier than mutex holder's and in this case we set mutex
holder to be dl_boosted. However, since RT 'dynamic' deadlines are only
initialized if such tasks get boosted at some point (or if they become
DEADLINE of course), in general RT 'dynamic' deadlines are usually equal
to 0 and this verifies the aforementioned condition.

Fix it by checking that the potential donor task is actually (even if
temporary because in turn boosted) running at DEADLINE priority before
using its 'dynamic' deadline value.

Fixes: 2d3d891d3344 ("sched/deadline: Add SCHED_DEADLINE inheritance logic")
Reported-by: syzbot+119ba87189432ead09b4@syzkaller.appspotmail.com
Signed-off-by: Juri Lelli 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Reviewed-by: Daniel Bristot de Oliveira 
Tested-by: Daniel Wagner 
Link: https://lkml.kernel.org/r/20181119153201.GB2119@localhost.localdomain
Signed-off-by: Sasha Levin

kretprobe: Prevent triggering kretprobe from within kprobe_flush_task

2020-06-30T19:38:33+00:00

[ Upstream commit 9b38cc704e844e41d9cf74e647bff1d249512cb3 ]

Ziqian reported lockup when adding retprobe on _raw_spin_lock_irqsave.
My test was also able to trigger lockdep output:

 ============================================
 WARNING: possible recursive locking detected
 5.6.0-rc6+ #6 Not tainted
 --------------------------------------------
 sched-messaging/2767 is trying to acquire lock:
 ffffffff9a492798 (&(kretprobe_table_locks[i].lock)){-.-.}, at: kretprobe_hash_lock+0x52/0xa0

 but task is already holding lock:
 ffffffff9a491a18 (&(kretprobe_table_locks[i].lock)){-.-.}, at: kretprobe_trampoline+0x0/0x50

 other info that might help us debug this:
  Possible unsafe locking scenario:

        CPU0
        ----
   lock(&(kretprobe_table_locks[i].lock));
   lock(&(kretprobe_table_locks[i].lock));

  *** DEADLOCK ***

  May be due to missing lock nesting notation

 1 lock held by sched-messaging/2767:
  #0: ffffffff9a491a18 (&(kretprobe_table_locks[i].lock)){-.-.}, at: kretprobe_trampoline+0x0/0x50

 stack backtrace:
 CPU: 3 PID: 2767 Comm: sched-messaging Not tainted 5.6.0-rc6+ #6
 Call Trace:
  dump_stack+0x96/0xe0
  __lock_acquire.cold.57+0x173/0x2b7
  ? native_queued_spin_lock_slowpath+0x42b/0x9e0
  ? lockdep_hardirqs_on+0x590/0x590
  ? __lock_acquire+0xf63/0x4030
  lock_acquire+0x15a/0x3d0
  ? kretprobe_hash_lock+0x52/0xa0
  _raw_spin_lock_irqsave+0x36/0x70
  ? kretprobe_hash_lock+0x52/0xa0
  kretprobe_hash_lock+0x52/0xa0
  trampoline_handler+0xf8/0x940
  ? kprobe_fault_handler+0x380/0x380
  ? find_held_lock+0x3a/0x1c0
  kretprobe_trampoline+0x25/0x50
  ? lock_acquired+0x392/0xbc0
  ? _raw_spin_lock_irqsave+0x50/0x70
  ? __get_valid_kprobe+0x1f0/0x1f0
  ? _raw_spin_unlock_irqrestore+0x3b/0x40
  ? finish_task_switch+0x4b9/0x6d0
  ? __switch_to_asm+0x34/0x70
  ? __switch_to_asm+0x40/0x70

The code within the kretprobe handler checks for probe reentrancy,
so we won't trigger any _raw_spin_lock_irqsave probe in there.

The problem is in outside kprobe_flush_task, where we call:

  kprobe_flush_task
    kretprobe_table_lock
      raw_spin_lock_irqsave
        _raw_spin_lock_irqsave

where _raw_spin_lock_irqsave triggers the kretprobe and installs
kretprobe_trampoline handler on _raw_spin_lock_irqsave return.

The kretprobe_trampoline handler is then executed with already
locked kretprobe_table_locks, and first thing it does is to
lock kretprobe_table_locks ;-) the whole lockup path like:

  kprobe_flush_task
    kretprobe_table_lock
      raw_spin_lock_irqsave
        _raw_spin_lock_irqsave ---> probe triggered, kretprobe_trampoline installed

        ---> kretprobe_table_locks locked

        kretprobe_trampoline
          trampoline_handler
            kretprobe_hash_lock(current, &head, &flags);  <--- deadlock

Adding kprobe_busy_begin/end helpers that mark code with fake
probe installed to prevent triggering of another kprobe within
this code.

Using these helpers in kprobe_flush_task, so the probe recursion
protection check is hit and the probe is never set to prevent
above lockup.

Link: http://lkml.kernel.org/r/158927059835.27680.7011202830041561604.stgit@devnote2

Fixes: ef53d9c5e4da ("kprobes: improve kretprobe scalability with hashed locking")
Cc: Ingo Molnar 
Cc: "Gustavo A . R . Silva" 
Cc: Anders Roxell 
Cc: "Naveen N . Rao" 
Cc: Anil S Keshavamurthy 
Cc: David Miller 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: stable@vger.kernel.org
Reported-by: "Ziqian SUN (Zamir)" 
Acked-by: Masami Hiramatsu 
Signed-off-by: Jiri Olsa 
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Sasha Levin