After the previous patch to remove sane_behavior support from
non-default hierarchies, CGRP_ROOT_SANE_BEHAVIOR is used only to
indicate the default hierarchy while parsing mount options.  This
patch makes the following cleanups around it.

* Don't show it in the mount option.  Eventually the default hierarchy
  will be assigned a different filesystem type.

* As sane_behavior is no longer effective on non-default hierarchies
  and the default hierarchy doesn't accept any mount options,
  parse_cgroupfs_options() can consider sane_behavior mount option as
  indicating the default hierarchy and fail if any other options are
  specified with it.  While at it, remove one of the double blank
  lines in the function.

* cgroup_mount() can now simply test CGRP_ROOT_SANE_BEHAVIOR to tell
  whether to mount the default hierarchy or not.

* As CGROUP_ROOT_SANE_BEHAVIOR's only role now is indicating whether
  to select the default hierarchy or not during mount, it doesn't need
  to be set in the default hierarchy itself.  cgroup_init_early()
  updated accordingly.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>

sane_behavior has been used as a development vehicle for the default
unified hierarchy.  Now that the default hierarchy is in place, the
flag became redundant and confusing as its usage is allowed on all
hierarchies.  There are gonna be either the default hierarchy or
legacy ones.  Let's make that clear by removing sane_behavior support
on non-default hierarchies.

This patch replaces cgroup_sane_behavior() with cgroup_on_dfl().  The
comment on top of CGRP_ROOT_SANE_BEHAVIOR is moved to on top of
cgroup_on_dfl() with sane_behavior specific part dropped.

On the default and legacy hierarchies w/o sane_behavior, this
shouldn't cause any behavior differences.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Acked-by: NLi Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>

"cgroup.sane_behavior" is added to help distinguishing whether
sane_behavior is in effect or not.  We now have the default hierarchy
where the flag is always in effect and are planning to remove
supporting sane behavior on the legacy hierarchies making this file on
the default hierarchy rather pointless.  Let's make it legacy only and
thus always zero.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>

cgroup_root->flags only contains CGRP_ROOT_* flags and there's no
reason to mask the flags.  Remove CGRP_ROOT_OPTION_MASK.

This doesn't cause any behavior differences.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>

Currently, the blkio subsystem attributes all of writeback IOs to the
root.  One of the issues is that there's no way to tell who originated
a writeback IO from block layer.  Those IOs are usually issued
asynchronously from a task which didn't have anything to do with
actually generating the dirty pages.  The memory subsystem, when
enabled, already keeps track of the ownership of each dirty page and
it's desirable for blkio to piggyback instead of adding its own
per-page tag.

blkio piggybacking on memory is an implementation detail which
preferably should be handled automatically without requiring explicit
userland action.  To achieve that, this patch implements
cgroup_subsys->depends_on which contains the mask of subsystems which
should be enabled together when the subsystem is enabled.

The previous patches already implemented the support for enabled but
invisible subsystems and cgroup_subsys->depends_on can be easily
implemented by updating cgroup_refresh_child_subsys_mask() so that it
calculates cgroup->child_subsys_mask considering
cgroup_subsys->depends_on of the explicitly enabled subsystems.

Documentation/cgroups/unified-hierarchy.txt is updated to explain that
subsystems may not become immediately available after being unused
from userland and that dependency could be a factor in it.  As
subsystems may already keep residual references, this doesn't
significantly change how subsystem rebinding can be used.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>

cgroup is implementing support for subsystem dependency which would
require a way to enable a subsystem even when it's not directly
configured through "cgroup.subtree_control".

The previous patches added support for explicitly and implicitly
enabled subsystems and showing/hiding their interface files.  An
explicitly enabled subsystem may become implicitly enabled if it's
turned off through "cgroup.subtree_control" but there are subsystems
depending on it.  In such cases, the subsystem, as it's turned off
when seen from userland, shouldn't enforce any resource control.
Also, the subsystem may be explicitly turned on later again and its
interface files should be as close to the intial state as possible.

This patch adds cgroup_subsys->css_reset() which is invoked when a css
is hidden.  The callback should disable resource control and reset the
state to the vanilla state.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>

cgroup is implementing support for subsystem dependency which would
require a way to enable a subsystem even when it's not directly
configured through "cgroup.subtree_control".

The preceding patch distinguished cgroup->subtree_control and
->child_subsys_mask where the former is the subsystems explicitly
configured by the userland and the latter is all enabled subsystems
currently is equal to the former but will include subsystems
implicitly enabled through dependency.

Subsystems which are enabled due to dependency shouldn't be visible to
userland.  This patch updates cgroup_subtree_control_write() and
create_css() such that interface files are not created for implicitly
enabled subsytems.

* @visible paramter is added to create_css().  Interface files are
  created only when true.

* If an already implicitly enabled subsystem is turned on through
  "cgroup.subtree_control", the existing css should be used.  css
  draining is skipped.

* cgroup_subtree_control_write() computes the new target
  cgroup->child_subsys_mask and create/kill or show/hide csses
  accordingly.

As the two subsystem masks are still kept identical, this patch
doesn't introduce any behavior changes.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>

cgroup is implementing support for subsystem dependency which would
require a way to enable a subsystem even when it's not directly
configured through "cgroup.subtree_control".

Previously, cgroup->child_subsys_mask directly reflected
"cgroup.subtree_control" and the enabled subsystems in the child
cgroups.  This patch adds cgroup->subtree_control which
"cgroup.subtree_control" operates on.  cgroup->child_subsys_mask is
now calculated from cgroup->subtree_control by
cgroup_refresh_child_subsys_mask(), which sets it identical to
cgroup->subtree_control for now.

This will allow using cgroup->child_subsys_mask for all the enabled
subsystems including the implicit ones and ->subtree_control for
tracking the explicitly requested ones.  This patch keeps the two
masks identical and doesn't introduce any behavior changes.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>

Make the following two reorganizations to
cgroup_subtree_control_write().  These are to prepare for future
changes and shouldn't cause any functional difference.

* Move availability above css offlining wait.

* Move cgrp->child_subsys_mask update above new css creation.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>

Changes kASLR from being compile-time selectable (blocked by
CONFIG_HIBERNATION), to being boot-time selectable (with hibernation
available by default) via the "kaslr" kernel command line.
Signed-off-by: NKees Cook <keescook@chromium.org>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

To support using kernel features that are not compatible with hibernation,
this creates the "nohibernate" kernel boot parameter to disable both
hibernation and resume. This allows hibernation support to be a boot-time
choice instead of only a compile-time choice.
Signed-off-by: NKees Cook <keescook@chromium.org>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

When the rtmutex fast path is enabled the slow unlock function can
create the following situation:

spin_lock(foo->m->wait_lock);
foo->m->owner = NULL;
	    			rt_mutex_lock(foo->m); <-- fast path
				free = atomic_dec_and_test(foo->refcnt);
				rt_mutex_unlock(foo->m); <-- fast path
				if (free)
				   kfree(foo);

spin_unlock(foo->m->wait_lock); <--- Use after free.

Plug the race by changing the slow unlock to the following scheme:

     while (!rt_mutex_has_waiters(m)) {
     	    /* Clear the waiters bit in m->owner */
	    clear_rt_mutex_waiters(m);
      	    owner = rt_mutex_owner(m);
      	    spin_unlock(m->wait_lock);
      	    if (cmpxchg(m->owner, owner, 0) == owner)
      	       return;
      	    spin_lock(m->wait_lock);
     }

So in case of a new waiter incoming while the owner tries the slow
path unlock we have two situations:

 unlock(wait_lock);
					lock(wait_lock);
 cmpxchg(p, owner, 0) == owner
 	    	   			mark_rt_mutex_waiters(lock);
	 				acquire(lock);

Or:

 unlock(wait_lock);
					lock(wait_lock);
	 				mark_rt_mutex_waiters(lock);
 cmpxchg(p, owner, 0) != owner
					enqueue_waiter();
					unlock(wait_lock);
 lock(wait_lock);
 wakeup_next waiter();
 unlock(wait_lock);
					lock(wait_lock);
					acquire(lock);

If the fast path is disabled, then the simple

   m->owner = NULL;
   unlock(m->wait_lock);

is sufficient as all access to m->owner is serialized via
m->wait_lock;

Also document and clarify the wakeup_next_waiter function as suggested
by Oleg Nesterov.
Reported-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140611183852.937945560@linutronix.de
Cc: stable@vger.kernel.org
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

This essentially reverts commit:

  ecd50f71 ("kprobes, x86: Call exception_enter after kprobes handled")

since it causes build errors with CONFIG_CONTEXT_TRACKING and
that has been made from misunderstandings;
context_track_user_*() don't involve much in interrupt context,
it just returns if in_interrupt() is true.

Instead of changing the do_debug/int3(), this just adds
context_track_user_*() to kprobes blacklist, since those are
still can be called right before kprobes handles int3 and debug
exceptions, and probing those will cause an infinite loop.
Reported-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>
Link: http://lkml.kernel.org/r/20140614064711.7865.45957.stgit@kbuild-fedora.novalocalSigned-off-by: NIngo Molnar <mingo@kernel.org>

This patch handles the gcov-related changes in GCC 4.9:

  A new counter (time profile) is added. The total number is 9 now.

  A new profile merge function __gcov_merge_time_profile is added.

See gcc/gcov-io.h and libgcc/libgcov-merge.c

For the first change, the layout of struct gcov_info is affected.

For the second one, a dummy function is added to kernel/gcov/base.c
similarly.
Signed-off-by: NYuan Pengfei <coolypf@qq.com>
Acked-by: NPeter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The kernel has no concept of capabilities with respect to inodes; inodes
exist independently of namespaces.  For example, inode_capable(inode,
CAP_LINUX_IMMUTABLE) would be nonsense.

This patch changes inode_capable to check for uid and gid mappings and
renames it to capable_wrt_inode_uidgid, which should make it more
obvious what it does.

Fixes CVE-2014-4014.

Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Serge Hallyn <serge.hallyn@ubuntu.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: stable@vger.kernel.org
Signed-off-by: NAndy Lutomirski <luto@amacapital.net>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The check that tests if ftrace_trace_arrays is empty in
top_trace_array(), uses the .prev pointer:

  if (list_empty(ftrace_trace_arrays.prev))

instead of testing the variable itself:

  if (list_empty(&ftrace_trace_arrays))

Although it is technically correct, it is awkward and confusing.
Use the proper method.

Link: http://lkml.kernel.org/r/87oay1bas8.fsf@sejong.aot.lge.comReported-by: NNamhyung Kim <namhyung@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The freeing of an instance, if max data is configured, there will be
per cpu data structures created. But these are not freed when the instance
is deleted, which causes a memory leak.

A new helper function is added that frees the individual buffers within a
trace array, instead of duplicating the code. This way changes made for one
are applied to the other (normal buffer vs max buffer).

Link: http://lkml.kernel.org/r/87k38pbake.fsf@sejong.aot.lge.comReported-by: NNamhyung Kim <namhyung@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Fixes an easy DoS and possible information disclosure.

This does nothing about the broken state of x32 auditing.

eparis: If the admin has enabled auditd and has specifically loaded
audit rules.  This bug has been around since before git.  Wow...

Cc: stable@vger.kernel.org
Signed-off-by: NAndy Lutomirski <luto@amacapital.net>
Signed-off-by: NEric Paris <eparis@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The recent addition of saved_cmdlines_size file had some remaining
(minor - mostly coding style) issues.  Fix them by passing pointer
name to sizeof() and using scnprintf().

Link: http://lkml.kernel.org/p/1402384295-23680-1-git-send-email-namhyung@kernel.org

Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Signed-off-by: NNamhyung Kim <namhyung@kernel.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The per_cpu buffers are created one per possible CPU. But these do
not mean that those CPUs are online, nor do they even exist.

With the addition of the ring buffer polling, it assumes that the
caller polls on an existing buffer. But this is not the case if
the user reads trace_pipe from a CPU that does not exist, and this
causes the kernel to crash.

Simple fix is to check the cpu against buffer bitmask against to see
if the buffer was allocated or not and return -ENODEV if it is
not.

More updates were done to pass the -ENODEV back up to userspace.

Link: http://lkml.kernel.org/r/5393DB61.6060707@oracle.comReported-by: NSasha Levin <sasha.levin@oracle.com>
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

This reverts commit 3090ffb5.

Re-enable the mmap2 interface as we will have a user soon.

Since things have changed since perf disabled mmap2, small tweaks
to the revert had to be done:

o commit 9d4ecc88 forced (n!=8) to become (n<7)
o a new libunwind test needed updating to use mmap2 interface
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Link: http://lkml.kernel.org/r/1401461382-209586-1-git-send-email-dzickus@redhat.comSigned-off-by: NJiri Olsa <jolsa@kernel.org>

The mmap2 interface was missing the protection and flags bits needed to
accurately determine if a mmap memory area was shared or private and
if it was readable or not.
Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
[tweaked patch to compile and wrote changelog]
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Link: http://lkml.kernel.org/r/1400526833-141779-2-git-send-email-dzickus@redhat.comSigned-off-by: NJiri Olsa <jolsa@kernel.org>

This function is supposed to return true if the new load imbalance is
worse than the old one.  It didn't.  I can only hope brown paper bags
are in style.

Now things converge much better on both the 4 node and 8 node systems.

I am not sure why this did not seem to impact specjbb performance on the
4 node system, which is the system I have full-time access to.

This bug was introduced recently, with commit e63da036 ("sched/numa:
Allow task switch if load imbalance improves")
Signed-off-by: NRik van Riel <riel@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When we walk the lock chain, we drop all locks after each step. So the
lock chain can change under us before we reacquire the locks. That's
harmless in principle as we just follow the wrong lock path. But it
can lead to a false positive in the dead lock detection logic:

T0 holds L0
T0 blocks on L1 held by T1
T1 blocks on L2 held by T2
T2 blocks on L3 held by T3
T4 blocks on L4 held by T4

Now we walk the chain

lock T1 -> lock L2 -> adjust L2 -> unlock T1 -> 
     lock T2 ->  adjust T2 ->  drop locks

T2 times out and blocks on L0

Now we continue:

lock T2 -> lock L0 -> deadlock detected, but it's not a deadlock at all.

Brad tried to work around that in the deadlock detection logic itself,
but the more I looked at it the less I liked it, because it's crystal
ball magic after the fact.

We actually can detect a chain change very simple:

lock T1 -> lock L2 -> adjust L2 -> unlock T1 -> lock T2 -> adjust T2 ->

     next_lock = T2->pi_blocked_on->lock;

drop locks

T2 times out and blocks on L0

Now we continue:

lock T2 -> 

     if (next_lock != T2->pi_blocked_on->lock)
     	   return;

So if we detect that T2 is now blocked on a different lock we stop the
chain walk. That's also correct in the following scenario:

lock T1 -> lock L2 -> adjust L2 -> unlock T1 -> lock T2 -> adjust T2 ->

     next_lock = T2->pi_blocked_on->lock;

drop locks

T3 times out and drops L3
T2 acquires L3 and blocks on L4 now

Now we continue:

lock T2 -> 

     if (next_lock != T2->pi_blocked_on->lock)
     	   return;

We don't have to follow up the chain at that point, because T2
propagated our priority up to T4 already.

[ Folded a cleanup patch from peterz ]
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reported-by: NBrad Mouring <bmouring@ni.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140605152801.930031935@linutronix.de
Cc: stable@vger.kernel.org

Even in the case when deadlock detection is not requested by the
caller, we can detect deadlocks. Right now the code stops the lock
chain walk and keeps the waiter enqueued, even on itself. Silly not to
yell when such a scenario is detected and to keep the waiter enqueued.

Return -EDEADLK unconditionally and handle it at the call sites.

The futex calls return -EDEADLK. The non futex ones dequeue the
waiter, throw a warning and put the task into a schedule loop.

Tagged for stable as it makes the code more robust.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Brad Mouring <bmouring@ni.com>
Link: http://lkml.kernel.org/r/20140605152801.836501969@linutronix.de
Cc: stable@vger.kernel.org
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

When an instance is created, it also gets a snapshot ring buffer
allocated (with minimum of pages). But when it is deleted the snapshot
buffer is not. There was a helper function added to match the allocation
of these ring buffers to a way to free them, but it wasn't used by
the deletion of an instance. Using that helper function solves this
memory leak.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

This typedef is unnecessary and should just be removed.
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

+ fix small typo
Signed-off-by: NFabian Frederick <fabf@skynet.be>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

trailing whitespace
Signed-off-by: NPaul McQuade <paulmcquad@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use #include <linux/uaccess.h> instead of <asm/uaccess.h>
Use #include <linux/types.h> instead of <asm/types.h>
Signed-off-by: NPaul McQuade <paulmcquad@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

schedstr, sleepstr and kvmstr are only used in strcmp & strlen
Signed-off-by: NFabian Frederick <fabf@skynet.be>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NFabian Frederick <fabf@skynet.be>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

-uid->gid
-split some function declarations
-if/then/else warning
Signed-off-by: NFabian Frederick <fabf@skynet.be>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When writing to a sysctl string, each write, regardless of VFS position,
begins writing the string from the start.  This means the contents of
the last write to the sysctl controls the string contents instead of the
first:

  open("/proc/sys/kernel/modprobe", O_WRONLY)   = 1
  write(1, "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"..., 4096) = 4096
  write(1, "/bin/true", 9)                = 9
  close(1)                                = 0

  $ cat /proc/sys/kernel/modprobe
  /bin/true

Expected behaviour would be to have the sysctl be "AAAA..." capped at
maxlen (in this case KMOD_PATH_LEN: 256), instead of truncating to the
contents of the second write.  Similarly, multiple short writes would
not append to the sysctl.

The old behavior is unlike regular POSIX files enough that doing audits
of software that interact with sysctls can end up in unexpected or
dangerous situations.  For example, "as long as the input starts with a
trusted path" turns out to be an insufficient filter, as what must also
happen is for the input to be entirely contained in a single write
syscall -- not a common consideration, especially for high level tools.

This provides kernel.sysctl_writes_strict as a way to make this behavior
act in a less surprising manner for strings, and disallows non-zero file
position when writing numeric sysctls (similar to what is already done
when reading from non-zero file positions).  For now, the default (0) is
to warn about non-zero file position use, but retain the legacy
behavior.  Setting this to -1 disables the warning, and setting this to
1 enables the file position respecting behavior.

[akpm@linux-foundation.org: fix build]
[akpm@linux-foundation.org: move misplaced hunk, per Randy]
Signed-off-by: NKees Cook <keescook@chromium.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Consolidate buffer length checking with new-line/end-of-line checking.
Additionally, instead of reading user memory twice, just do the
assignment during the loop.

This change doesn't affect the potential races here.  It was already
possible to read a sysctl that was in the middle of a write.  In both
cases, the string will always be NULL terminated.  The pre-existing race
remains a problem to be solved.
Signed-off-by: NKees Cook <keescook@chromium.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When writing to a sysctl string, each write, regardless of VFS position,
began writing the string from the start.  This meant the contents of the
last write to the sysctl controlled the string contents instead of the
first.

This misbehavior was featured in an exploit against Chrome OS.  While
it's not in itself a vulnerability, it's a weirdness that isn't on the
mind of most auditors: "This filter looks correct, the first line
written would not be meaningful to sysctl" doesn't apply here, since the
size of the write and the contents of the final write are what matter
when writing to sysctls.

This adds the sysctl kernel.sysctl_writes_strict to control the write
behavior.  The default (0) reports when VFS position is non-0 on a
write, but retains legacy behavior, -1 disables the warning, and 1
enables the position-respecting behavior.

The long-term plan here is to wait for userspace to be fixed in response
to the new warning and to then switch the default kernel behavior to the
new position-respecting behavior.

This patch (of 4):

The char buffer arguments are needlessly cast in weird places.  Clean it
up so things are easier to read.
Signed-off-by: NKees Cook <keescook@chromium.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

+ some pr_warning -> pr_warn and checkpatch warning fixes
Signed-off-by: NFabian Frederick <fabf@skynet.be>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add a "crash_kexec_post_notifiers" boot option to run kdump after
running panic_notifiers and dump kmsg.  This can help rare situations
where kdump fails because of unstable crashed kernel or hardware failure
(memory corruption on critical data/code), or the 2nd kernel is already
broken by the 1st kernel (it's a broken behavior, but who can guarantee
that the "crashed" kernel works correctly?).

Usage: add "crash_kexec_post_notifiers" to kernel boot option.

Note that this actually increases risks of the failure of kdump.  This
option should be set only if you worry about the rare case of kdump
failure rather than increasing the chance of success.
Signed-off-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: NMotohiro Kosaki <Motohiro.Kosaki@us.fujitsu.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Cc: Satoru MORIYA <satoru.moriya.br@hitachi.com>
Cc: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There is a longstanding problem related to CPU hotplug which causes IPIs
to be delivered to offline CPUs, and the smp-call-function IPI handler
code prints out a warning whenever this is detected.  Every once in a
while this (usually harmless) warning gets reported on LKML, but so far
it has not been completely fixed.  Usually the solution involves finding
out the IPI sender and fixing it by adding appropriate synchronization
with CPU hotplug.

However, while going through one such internal bug reports, I found that
there is a significant bug in the receiver side itself (more
specifically, in stop-machine) that can lead to this problem even when
the sender code is perfectly fine.  This patchset fixes that
synchronization problem in the CPU hotplug stop-machine code.

Patch 1 adds some additional debug code to the smp-call-function
framework, to help debug such issues easily.

Patch 2 modifies the stop-machine code to ensure that any IPIs that were
sent while the target CPU was online, would be noticed and handled by
that CPU without fail before it goes offline.  Thus, this avoids
scenarios where IPIs are received on offline CPUs (as long as the sender
uses proper hotplug synchronization).

In fact, I debugged the problem by using Patch 1, and found that the
payload of the IPI was always the block layer's trigger_softirq()
function.  But I was not able to find anything wrong with the block
layer code.  That's when I started looking at the stop-machine code and
realized that there is a race-window which makes the IPI _receiver_ the
culprit, not the sender.  Patch 2 fixes that race and hence this should
put an end to most of the hard-to-debug IPI-to-offline-CPU issues.

This patch (of 2):

Today the smp-call-function code just prints a warning if we get an IPI
on an offline CPU.  This info is sufficient to let us know that
something went wrong, but often it is very hard to debug exactly who
sent the IPI and why, from this info alone.

In most cases, we get the warning about the IPI to an offline CPU,
immediately after the CPU going offline comes out of the stop-machine
phase and reenables interrupts.  Since all online CPUs participate in
stop-machine, the information regarding the sender of the IPI is already
lost by the time we exit the stop-machine loop.  So even if we dump the
stack on each CPU at this point, we won't find anything useful since all
of them will show the stack-trace of the stopper thread.  So we need a
better way to figure out who sent the IPI and why.

To achieve this, when we detect an IPI targeted to an offline CPU, loop
through the call-single-data linked list and print out the payload
(i.e., the name of the function which was supposed to be executed by the
target CPU).  This would give us an insight as to who might have sent
the IPI and help us debug this further.

[akpm@linux-foundation.org: correctly suppress warning output on second and later occurrences]
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mike Galbraith <mgalbraith@suse.de>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Now that we have kernel_sigaction() we can change wait_for_helper() to
use it and cleans up the code a bit.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>