linux-stable.git/kernel, branch v3.4.38

nohz: Make tick_nohz_irq_exit() irq safe

2013-03-28T19:12:27+00:00

commit e5ab012c3271990e8457055c25cafddc1ae8aa6b upstream.

As it stands, irq_exit() may or may not be called with
irqs disabled, depending on __ARCH_IRQ_EXIT_IRQS_DISABLED
that the arch can define.

It makes tick_nohz_irq_exit() unsafe. For example two
interrupts can race in tick_nohz_stop_sched_tick(): the inner
most one computes the expiring time on top of the timer list,
then it's interrupted right before reprogramming the
clock. The new interrupt enqueues a new timer list timer,
it reprogram the clock to take it into account and it exits.
The CPUs resumes the inner most interrupt and performs the clock
reprogramming without considering the new timer list timer.

This regression has been introduced by:
     280f06774afedf849f0b34248ed6aff57d0f6908
     ("nohz: Separate out irq exit and idle loop dyntick logic")

Let's fix it right now with the appropriate protections.

A saner long term solution will be to remove
__ARCH_IRQ_EXIT_IRQS_DISABLED and mandate that irq_exit() is called
with interrupts disabled.

Signed-off-by: Frederic Weisbecker 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/1361373336-11337-1-git-send-email-fweisbec@gmail.com
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Lingzhu Xiang 
Reviewed-by: CAI Qian 
Signed-off-by: Greg Kroah-Hartman

clockevents: Don't allow dummy broadcast timers

2013-03-28T19:12:26+00:00

commit a7dc19b8652c862d5b7c4d2339bd3c428bd29c4a upstream.

Currently tick_check_broadcast_device doesn't reject clock_event_devices
with CLOCK_EVT_FEAT_DUMMY, and may select them in preference to real
hardware if they have a higher rating value. In this situation, the
dummy timer is responsible for broadcasting to itself, and the core
clockevents code may attempt to call non-existent callbacks for
programming the dummy, eventually leading to a panic.

This patch makes tick_check_broadcast_device always reject dummy timers,
preventing this problem.

Signed-off-by: Mark Rutland 
Cc: linux-arm-kernel@lists.infradead.org
Cc: Jon Medhurst (Tixy) 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

tracing: Fix free of probe entry by calling call_rcu_sched()

2013-03-28T19:12:06+00:00

commit 740466bc89ad8bd5afcc8de220f715f62b21e365 upstream.

Because function tracing is very invasive, and can even trace
calls to rcu_read_lock(), RCU access in function tracing is done
with preempt_disable_notrace(). This requires a synchronize_sched()
for updates and not a synchronize_rcu().

Function probes (traceon, traceoff, etc) must be freed after
a synchronize_sched() after its entry has been removed from the
hash. But call_rcu() is used. Fix this by using call_rcu_sched().

Also fix the usage to use hlist_del_rcu() instead of hlist_del().

Signed-off-by: Steven Rostedt 
Cc: Paul McKenney 
Signed-off-by: Greg Kroah-Hartman

tracing: Fix race in snapshot swapping

2013-03-28T19:12:06+00:00

commit 2721e72dd10f71a3ba90f59781becf02638aa0d9 upstream.

Although the swap is wrapped with a spin_lock, the assignment
of the temp buffer used to swap is not within that lock.
It needs to be moved into that lock, otherwise two swaps
happening on two different CPUs, can end up using the wrong
temp buffer to assign in the swap.

Luckily, all current callers of the swap function appear to have
their own locks. But in case something is added that allows two
different callers to call the swap, then there's a chance that
this race can trigger and corrupt the buffers.

New code is coming soon that will allow for this race to trigger.

I've Cc'd stable, so this bug will not show up if someone backports
one of the changes that can trigger this bug.

Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

signal: always clear sa_restorer on execve

2013-03-20T20:04:58+00:00

commit 2ca39528c01a933f6689cd6505ce65bd6d68a530 upstream.

When the new signal handlers are set up, the location of sa_restorer is
not cleared, leaking a parent process's address space location to
children.  This allows for a potential bypass of the parent's ASLR by
examining the sa_restorer value returned when calling sigaction().

Based on what should be considered "secret" about addresses, it only
matters across the exec not the fork (since the VMAs haven't changed
until the exec).  But since exec sets SIG_DFL and keeps sa_restorer,
this is where it should be fixed.

Given the few uses of sa_restorer, a "set" function was not written
since this would be the only use.  Instead, we use
__ARCH_HAS_SA_RESTORER, as already done in other places.

Example of the leak before applying this patch:

  $ cat /proc/$$/maps
  ...
  7fb9f3083000-7fb9f3238000 r-xp 00000000 fd:01 404469 .../libc-2.15.so
  ...
  $ ./leak
  ...
  7f278bc74000-7f278be29000 r-xp 00000000 fd:01 404469 .../libc-2.15.so
  ...
  1 0 (nil) 0x7fb9f30b94a0
  2 4000000 (nil) 0x7f278bcaa4a0
  3 4000000 (nil) 0x7f278bcaa4a0
  4 0 (nil) 0x7fb9f30b94a0
  ...

[akpm@linux-foundation.org: use SA_RESTORER for backportability]
Signed-off-by: Kees Cook 
Reported-by: Emese Revfy 
Cc: Emese Revfy 
Cc: PaX Team 
Cc: Al Viro 
Cc: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Cc: Serge Hallyn 
Cc: Julien Tinnes 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

ftrace: Update the kconfig for DYNAMIC_FTRACE

2013-03-14T18:29:51+00:00

commit db05021d49a994ee40a9735d9c3cb0060c9babb8 upstream.

The prompt to enable DYNAMIC_FTRACE (the ability to nop and
enable function tracing at run time) had a confusing statement:

 "enable/disable ftrace tracepoints dynamically"

This was written before tracepoints were added to the kernel,
but now that tracepoints have been added, this is very confusing
and has confused people enough to give wrong information during
presentations.

Not only that, I looked at the help text, and it still references
that dreaded daemon that use to wake up once a second to update
the nop locations and brick NICs, that hasn't been around for over
five years.

Time to bring the text up to the current decade.

Reported-by: Ezequiel Garcia 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

cgroup: fix exit() vs rmdir() race

2013-03-03T22:06:44+00:00

commit 71b5707e119653039e6e95213f00479668c79b75 upstream.

In cgroup_exit() put_css_set_taskexit() is called without any lock,
which might lead to accessing a freed cgroup:

thread1                           thread2
---------------------------------------------
exit()
  cgroup_exit()
    put_css_set_taskexit()
      atomic_dec(cgrp->count);
                                   rmdir();
      /* not safe !! */
      check_for_release(cgrp);

rcu_read_lock() can be used to make sure the cgroup is alive.

Signed-off-by: Li Zefan 
Signed-off-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

cpuset: fix cpuset_print_task_mems_allowed() vs rename() race

2013-03-03T22:06:44+00:00

commit 63f43f55c9bbc14f76b582644019b8a07dc8219a upstream.

rename() will change dentry->d_name. The result of this race can
be worse than seeing partially rewritten name, but we might access
a stale pointer because rename() will re-allocate memory to hold
a longer name.

It's safe in the protection of dentry->d_lock.

v2: check NULL dentry before acquiring dentry lock.

Signed-off-by: Li Zefan 
Signed-off-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

sysctl: fix null checking in bin_dn_node_address()

2013-03-03T22:06:41+00:00

commit df1778be1a33edffa51d094eeda87c858ded6560 upstream.

The null check of `strchr() + 1' is broken, which is always non-null,
leading to OOB read.  Instead, check the result of strchr().

Signed-off-by: Xi Wang 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

ftrace: Call ftrace cleanup module notifier after all other notifiers

2013-03-03T22:06:38+00:00

commit 8c189ea64eea01ca20d102ddb74d6936dd16c579 upstream.

Commit: c1bf08ac "ftrace: Be first to run code modification on modules"

changed ftrace module notifier's priority to INT_MAX in order to
process the ftrace nops before anything else could touch them
(namely kprobes). This was the correct thing to do.

Unfortunately, the ftrace module notifier also contains the ftrace
clean up code. As opposed to the set up code, this code should be
run *after* all the module notifiers have run in case a module is doing
correct clean-up and unregisters its ftrace hooks. Basically, ftrace
needs to do clean up on module removal, as it needs to know about code
being removed so that it doesn't try to modify that code. But after it
removes the module from its records, if a ftrace user tries to remove
a probe, that removal will fail due as the record of that code segment
no longer exists.

Nothing really bad happens if the probe removal is called after ftrace
did the clean up, but the ftrace removal function will return an error.
Correct code (such as kprobes) will produce a WARN_ON() if it fails
to remove the probe. As people get annoyed by frivolous warnings, it's
best to do the ftrace clean up after everything else.

By splitting the ftrace_module_notifier into two notifiers, one that
does the module load setup that is run at high priority, and the other
that is called for module clean up that is run at low priority, the
problem is solved.

Reported-by: Frank Ch. Eigler 
Acked-by: Masami Hiramatsu 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman