linux-toradex.git/kernel, branch v4.4.61

ring-buffer: Fix return value check in test_ringbuffer()

2017-04-12T10:38:33+00:00

commit 62277de758b155dc04b78f195a1cb5208c37b2df upstream.

In case of error, the function kthread_run() returns ERR_PTR()
and never returns NULL. The NULL test in the return value check
should be replaced with IS_ERR().

Link: http://lkml.kernel.org/r/1466184839-14927-1-git-send-email-weiyj_lk@163.com

Fixes: 6c43e554a ("ring-buffer: Add ring buffer startup selftest")
Signed-off-by: Wei Yongjun 
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Greg Kroah-Hartman

ptrace: fix PTRACE_LISTEN race corrupting task->state

2017-04-12T10:38:33+00:00

commit 5402e97af667e35e54177af8f6575518bf251d51 upstream.

In PT_SEIZED + LISTEN mode STOP/CONT signals cause a wakeup against
__TASK_TRACED.  If this races with the ptrace_unfreeze_traced at the end
of a PTRACE_LISTEN, this can wake the task /after/ the check against
__TASK_TRACED, but before the reset of state to TASK_TRACED.  This
causes it to instead clobber TASK_WAKING, allowing a subsequent wakeup
against TRACED while the task is still on the rq wake_list, corrupting
it.

Oleg said:
 "The kernel can crash or this can lead to other hard-to-debug problems.
  In short, "task->state = TASK_TRACED" in ptrace_unfreeze_traced()
  assumes that nobody else can wake it up, but PTRACE_LISTEN breaks the
  contract. Obviusly it is very wrong to manipulate task->state if this
  task is already running, or WAKING, or it sleeps again"

[akpm@linux-foundation.org: coding-style fixes]
Fixes: 9899d11f ("ptrace: ensure arch_ptrace/ptrace_request can never race with SIGKILL")
Link: http://lkml.kernel.org/r/xm26y3vfhmkp.fsf_-_@bsegall-linux.mtv.corp.google.com
Signed-off-by: Ben Segall 
Acked-by: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

padata: avoid race in reordering

2017-04-08T07:53:32+00:00

commit de5540d088fe97ad583cc7d396586437b32149a5 upstream.

Under extremely heavy uses of padata, crashes occur, and with list
debugging turned on, this happens instead:

[87487.298728] WARNING: CPU: 1 PID: 882 at lib/list_debug.c:33
__list_add+0xae/0x130
[87487.301868] list_add corruption. prev->next should be next
(ffffb17abfc043d0), but was ffff8dba70872c80. (prev=ffff8dba70872b00).
[87487.339011]  [] dump_stack+0x68/0xa3
[87487.342198]  [] ? console_unlock+0x281/0x6d0
[87487.345364]  [] __warn+0xff/0x140
[87487.348513]  [] warn_slowpath_fmt+0x4a/0x50
[87487.351659]  [] __list_add+0xae/0x130
[87487.354772]  [] ? _raw_spin_lock+0x64/0x70
[87487.357915]  [] padata_reorder+0x1e6/0x420
[87487.361084]  [] padata_do_serial+0xa5/0x120

padata_reorder calls list_add_tail with the list to which its adding
locked, which seems correct:

spin_lock(&squeue->serial.lock);
list_add_tail(&padata->list, &squeue->serial.list);
spin_unlock(&squeue->serial.lock);

This therefore leaves only place where such inconsistency could occur:
if padata->list is added at the same time on two different threads.
This pdata pointer comes from the function call to
padata_get_next(pd), which has in it the following block:

next_queue = per_cpu_ptr(pd->pqueue, cpu);
padata = NULL;
reorder = &next_queue->reorder;
if (!list_empty(&reorder->list)) {
       padata = list_entry(reorder->list.next,
                           struct padata_priv, list);
       spin_lock(&reorder->lock);
       list_del_init(&padata->list);
       atomic_dec(&pd->reorder_objects);
       spin_unlock(&reorder->lock);

       pd->processed++;

       goto out;
}
out:
return padata;

I strongly suspect that the problem here is that two threads can race
on reorder list. Even though the deletion is locked, call to
list_entry is not locked, which means it's feasible that two threads
pick up the same padata object and subsequently call list_add_tail on
them at the same time. The fix is thus be hoist that lock outside of
that block.

Signed-off-by: Jason A. Donenfeld 
Acked-by: Steffen Klassert 
Signed-off-by: Herbert Xu 
Signed-off-by: Greg Kroah-Hartman

sched/rt: Add a missing rescheduling point

2017-03-31T07:49:54+00:00

commit 619bd4a71874a8fd78eb6ccf9f272c5e98bcc7b7 upstream.

Since the change in commit:

  fd7a4bed1835 ("sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks")

... we don't reschedule a task under certain circumstances:

Lets say task-A, SCHED_OTHER, is running on CPU0 (and it may run only on
CPU0) and holds a PI lock. This task is removed from the CPU because it
used up its time slice and another SCHED_OTHER task is running. Task-B on
CPU1 runs at RT priority and asks for the lock owned by task-A. This
results in a priority boost for task-A. Task-B goes to sleep until the
lock has been made available. Task-A is already runnable (but not active),
so it receives no wake up.

The reality now is that task-A gets on the CPU once the scheduler decides
to remove the current task despite the fact that a high priority task is
enqueued and waiting. This may take a long time.

The desired behaviour is that CPU0 immediately reschedules after the
priority boost which made task-A the task with the lowest priority.

Suggested-by: Peter Zijlstra 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Thomas Gleixner 
Fixes: fd7a4bed1835 ("sched, rt: Convert switched_{from, to}_rt() prio_changed_rt() to balance callbacks")
Link: http://lkml.kernel.org/r/20170124144006.29821-1-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

perf/core: Fix event inheritance on fork()

2017-03-26T10:13:18+00:00

commit e7cc4865f0f31698ef2f7aac01a50e78968985b7 upstream.

While hunting for clues to a use-after-free, Oleg spotted that
perf_event_init_context() can loose an error value with the result
that fork() can succeed even though we did not fully inherit the perf
event context.

Spotted-by: Oleg Nesterov 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnaldo Carvalho de Melo 
Cc: Dmitry Vyukov 
Cc: Frederic Weisbecker 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Mathieu Desnoyers 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Cc: Thomas Gleixner 
Cc: Vince Weaver 
Cc: oleg@redhat.com
Fixes: 889ff0150661 ("perf/core: Split context's event group list into pinned and non-pinned lists")
Link: http://lkml.kernel.org/r/20170316125823.190342547@infradead.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

kernek/fork.c: allocate idle task for a CPU always on its local node

2017-03-26T10:13:18+00:00

commit 725fc629ff2545b061407305ae51016c9f928fce upstream.

Linux preallocates the task structs of the idle tasks for all possible
CPUs.  This currently means they all end up on node 0.  This also
implies that the cache line of MWAIT, which is around the flags field in
the task struct, are all located in node 0.

We see a noticeable performance improvement on Knights Landing CPUs when
the cache lines used for MWAIT are located in the local nodes of the
CPUs using them.  I would expect this to give a (likely slight)
improvement on other systems too.

The patch implements placing the idle task in the node of its CPUs, by
passing the right target node to copy_process()

[akpm@linux-foundation.org: use NUMA_NO_NODE, not a bare -1]
Link: http://lkml.kernel.org/r/1463492694-15833-1-git-send-email-andi@firstfloor.org
Signed-off-by: Andi Kleen 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Cc: Sumit Semwal 
Signed-off-by: Greg Kroah-Hartman

futex: Add missing error handling to FUTEX_REQUEUE_PI

2017-03-22T11:04:19+00:00

commit 9bbb25afeb182502ca4f2c4f3f88af0681b34cae upstream.

Thomas spotted that fixup_pi_state_owner() can return errors and we
fail to unlock the rt_mutex in that case.

Reported-by: Thomas Gleixner 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Darren Hart 
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: dvhart@infradead.org
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170304093558.867401760@infradead.org
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

futex: Fix potential use-after-free in FUTEX_REQUEUE_PI

2017-03-22T11:04:19+00:00

commit c236c8e95a3d395b0494e7108f0d41cf36ec107c upstream.

While working on the futex code, I stumbled over this potential
use-after-free scenario. Dmitry triggered it later with syzkaller.

pi_mutex is a pointer into pi_state, which we drop the reference on in
unqueue_me_pi(). So any access to that pointer after that is bad.

Since other sites already do rt_mutex_unlock() with hb->lock held, see
for example futex_lock_pi(), simply move the unlock before
unqueue_me_pi().

Reported-by: Dmitry Vyukov 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Darren Hart 
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: dvhart@infradead.org
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170304093558.801744246@infradead.org
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

Fix: Disable sys_membarrier when nohz_full is enabled

2017-03-12T05:37:26+00:00

commit 907565337ebf998a68cb5c5b2174ce5e5da065eb upstream.

Userspace applications should be allowed to expect the membarrier system
call with MEMBARRIER_CMD_SHARED command to issue memory barriers on
nohz_full CPUs, but synchronize_sched() does not take those into
account.

Given that we do not want unrelated processes to be able to affect
real-time sensitive nohz_full CPUs, simply return ENOSYS when membarrier
is invoked on a kernel with enabled nohz_full CPUs.

Signed-off-by: Mathieu Desnoyers 
CC: Josh Triplett 
CC: Steven Rostedt 
Signed-off-by: Paul E. McKenney 
Cc: Frederic Weisbecker 
Cc: Chris Metcalf 
Cc: Rik van Riel 
Acked-by: Lai Jiangshan 
Reviewed-by: Josh Triplett 
Signed-off-by: Greg Kroah-Hartman

printk: use rcuidle console tracepoint

2017-02-23T16:43:10+00:00

commit fc98c3c8c9dcafd67adcce69e6ce3191d5306c9c upstream.

Use rcuidle console tracepoint because, apparently, it may be issued
from an idle CPU:

  hw-breakpoint: Failed to enable monitor mode on CPU 0.
  hw-breakpoint: CPU 0 failed to disable vector catch

  ===============================
  [ ERR: suspicious RCU usage.  ]
  4.10.0-rc8-next-20170215+ #119 Not tainted
  -------------------------------
  ./include/trace/events/printk.h:32 suspicious rcu_dereference_check() usage!

  other info that might help us debug this:

  RCU used illegally from idle CPU!
  rcu_scheduler_active = 2, debug_locks = 0
  RCU used illegally from extended quiescent state!
  2 locks held by swapper/0/0:
   #0:  (cpu_pm_notifier_lock){......}, at: [] cpu_pm_exit+0x10/0x54
   #1:  (console_lock){+.+.+.}, at: [] vprintk_emit+0x264/0x474

  stack backtrace:
  CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.10.0-rc8-next-20170215+ #119
  Hardware name: Generic OMAP4 (Flattened Device Tree)
    console_unlock
    vprintk_emit
    vprintk_default
    printk
    reset_ctrl_regs
    dbg_cpu_pm_notify
    notifier_call_chain
    cpu_pm_exit
    omap_enter_idle_coupled
    cpuidle_enter_state
    cpuidle_enter_state_coupled
    do_idle
    cpu_startup_entry
    start_kernel

This RCU warning, however, is suppressed by lockdep_off() in printk().
lockdep_off() increments the ->lockdep_recursion counter and thus
disables RCU_LOCKDEP_WARN() and debug_lockdep_rcu_enabled(), which want
lockdep to be enabled "current->lockdep_recursion == 0".

Link: http://lkml.kernel.org/r/20170217015932.11898-1-sergey.senozhatsky@gmail.com
Signed-off-by: Sergey Senozhatsky 
Reported-by: Tony Lindgren 
Tested-by: Tony Lindgren 
Acked-by: Paul E. McKenney 
Acked-by: Steven Rostedt (VMware) 
Cc: Petr Mladek 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Tony Lindgren 
Cc: Russell King 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman