Commit Graph

278 Commits

Author SHA1 Message Date
Ingo Molnar 6e84f31522 sched/headers: Prepare for new header dependencies before moving code to <linux/sched/mm.h>
We are going to split <linux/sched/mm.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/mm.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

The APIs that are going to be moved first are:

   mm_alloc()
   __mmdrop()
   mmdrop()
   mmdrop_async_fn()
   mmdrop_async()
   mmget_not_zero()
   mmput()
   mmput_async()
   get_task_mm()
   mm_access()
   mm_release()

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-03-02 08:42:28 +01:00
Ingo Molnar 84f001e157 sched/headers: Prepare for new header dependencies before moving code to <linux/sched/wake_q.h>
We are going to split <linux/sched/wake_q.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/wake_q.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-03-02 08:42:26 +01:00
Vegard Nossum f1f1007644 mm: add new mmgrab() helper
Apart from adding the helper function itself, the rest of the kernel is
converted mechanically using:

  git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)->mm_count);/mmgrab\(\1\);/'
  git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)\.mm_count);/mmgrab\(\&\1\);/'

This is needed for a later patch that hooks into the helper, but might
be a worthwhile cleanup on its own.

(Michal Hocko provided most of the kerneldoc comment.)

Link: http://lkml.kernel.org/r/20161218123229.22952-1-vegard.nossum@oracle.com
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-27 18:43:48 -08:00
Yang Yang 25f71d1c3e futex: Move futex_init() to core_initcall
The UEVENT user mode helper is enabled before the initcalls are executed
and is available when the root filesystem has been mounted.

The user mode helper is triggered by device init calls and the executable
might use the futex syscall.

futex_init() is marked __initcall which maps to device_initcall, but there
is no guarantee that futex_init() is invoked _before_ the first device init
call which triggers the UEVENT user mode helper.

If the user mode helper uses the futex syscall before futex_init() then the
syscall crashes with a NULL pointer dereference because the futex subsystem
has not been initialized yet.

Move futex_init() to core_initcall so futexes are initialized before the
root filesystem is mounted and the usermode helper becomes available.

[ tglx: Rewrote changelog ]

Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Cc: jiang.biao2@zte.com.cn
Cc: jiang.zhengxiong@zte.com.cn
Cc: zhong.weidong@zte.com.cn
Cc: deng.huali@zte.com.cn
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1483085875-6130-1-git-send-email-yang.yang29@zte.com.cn
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2017-02-13 16:12:22 +01:00
Thomas Gleixner 2456e85535 ktime: Get rid of the union
ktime is a union because the initial implementation stored the time in
scalar nanoseconds on 64 bit machine and in a endianess optimized timespec
variant for 32bit machines. The Y2038 cleanup removed the timespec variant
and switched everything to scalar nanoseconds. The union remained, but
become completely pointless.

Get rid of the union and just keep ktime_t as simple typedef of type s64.

The conversion was done with coccinelle and some manual mopping up.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
2016-12-25 17:21:22 +01:00
Waiman Long 194a6b5b9c sched/wake_q: Rename WAKE_Q to DEFINE_WAKE_Q
Currently the wake_q data structure is defined by the WAKE_Q() macro.
This macro, however, looks like a function doing something as "wake" is
a verb. Even checkpatch.pl was confused as it reported warnings like

  WARNING: Missing a blank line after declarations
  #548: FILE: kernel/futex.c:3665:
  +	int ret;
  +	WAKE_Q(wake_q);

This patch renames the WAKE_Q() macro to DEFINE_WAKE_Q() which clarifies
what the macro is doing and eliminates the checkpatch.pl warnings.

Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1479401198-1765-1-git-send-email-longman@redhat.com
[ Resolved conflict and added missing rename. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-11-21 10:29:01 +01:00
Thomas Gleixner e8b61b3f2c futex: Add some more function commentry
Add some more comments and reformat existing ones to kernel doc style.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Darren Hart <dvhart@linux.intel.com>
Link: http://lkml.kernel.org/r/1464770609-30168-1-git-send-email-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-09-05 17:20:18 +02:00
Thomas Gleixner 784bdf3bb6 futex: Assume all mappings are private on !MMU systems
To quote Rick why there is no need for shared mapping on !MMU systems:

|With MMU, shared futex keys need to identify the physical backing for
|a memory address because it may be mapped at different addresses in
|different processes (or even multiple times in the same process).
|Without MMU this cannot happen. You only have physical addresses. So
|the "private futex" behavior of using the virtual address as the key
|is always correct (for both shared and private cases) on nommu
|systems.

This patch disables the FLAGS_SHARED in a way that allows the compiler to
remove that code.

[bigeasy: Added changelog ]
Reported-by: Rich Felker <dalias@libc.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20160729143230.GA21715@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-07-29 18:44:14 +02:00
Mel Gorman 077fa7aed1 futex: Calculate the futex key based on a tail page for file-based futexes
Mike Galbraith reported that the LTP test case futex_wake04 was broken
by commit 65d8fc777f ("futex: Remove requirement for lock_page()
in get_futex_key()").

This test case uses futexes backed by hugetlbfs pages and so there is an
associated inode with a futex stored on such pages. The problem is that
the key is being calculated based on the head page index of the hugetlbfs
page and not the tail page.

Prior to the optimisation, the page lock was used to stabilise mappings and
pin the inode is file-backed which is overkill. If the page was a compound
page, the head page was automatically looked up as part of the page lock
operation but the tail page index was used to calculate the futex key.

After the optimisation, the compound head is looked up early and the page
lock is only relied upon to identify truncated pages, special pages or a
shmem page moving to swapcache. The head page is looked up because without
the page lock, special care has to be taken to pin the inode correctly.
However, the tail page is still required to calculate the futex key so
this patch records the tail page.

On vanilla 4.6, the output of the test case is;

futex_wake04    0  TINFO  :  Hugepagesize 2097152
futex_wake04    1  TFAIL  :  futex_wake04.c:126: Bug: wait_thread2 did not wake after 30 secs.

With the patch applied

futex_wake04    0  TINFO  :  Hugepagesize 2097152
futex_wake04    1  TPASS  :  Hi hydra, thread2 awake!

Fixes: 65d8fc777f "futex: Remove requirement for lock_page() in get_futex_key()"
Reported-and-tested-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20160608132522.GM2469@suse.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-06-08 19:23:54 +02:00
Linus Torvalds bd28b14591 x86: remove more uaccess_32.h complexity
I'm looking at trying to possibly merge the 32-bit and 64-bit versions
of the x86 uaccess.h implementation, but first this needs to be cleaned
up.

For example, the 32-bit version of "__copy_from_user_inatomic()" is
mostly the special cases for the constant size, and it's actually almost
never relevant.  Most users aren't actually using a constant size
anyway, and the few cases that do small constant copies are better off
just using __get_user() instead.

So get rid of the unnecessary complexity.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-22 17:21:27 -07:00
Davidlohr Bueso fe1bce9e21 futex: Acknowledge a new waiter in counter before plist
Otherwise an incoming waker on the dest hash bucket can miss
the waiter adding itself to the plist during the lockless
check optimization (small window but still the correct way
of doing this); similarly to the decrement counterpart.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: bigeasy@linutronix.de
Cc: dvhart@infradead.org
Cc: stable@kernel.org
Link: http://lkml.kernel.org/r/1461208164-29150-1-git-send-email-dave@stgolabs.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-04-21 11:06:09 +02:00
Sebastian Andrzej Siewior 89e9e66ba1 futex: Handle unlock_pi race gracefully
If userspace calls UNLOCK_PI unconditionally without trying the TID -> 0
transition in user space first then the user space value might not have the
waiters bit set. This opens the following race:

CPU0	    	      	    CPU1
uval = get_user(futex)
			    lock(hb)
lock(hb)
			    futex |= FUTEX_WAITERS
			    ....
			    unlock(hb)

cmpxchg(futex, uval, newval)

So the cmpxchg fails and returns -EINVAL to user space, which is wrong because
the futex value is valid.

To handle this (yes, yet another) corner case gracefully, check for a flag
change and retry.

[ tglx: Massaged changelog and slightly reworked implementation ]

Fixes: ccf9e6a80d ("futex: Make unlock_pi more robust")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: stable@vger.kernel.org
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1460723739-5195-1-git-send-email-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-04-20 12:33:13 +02:00
Jianyu Zhan 29b75eb2d5 futex: Replace barrier() in unqueue_me() with READ_ONCE()
Commit e91467ecd1 ("bug in futex unqueue_me") introduced a barrier() in
unqueue_me() to prevent the compiler from rereading the lock pointer which
might change after a check for NULL.

Replace the barrier() with a READ_ONCE() for the following reasons:

1) READ_ONCE() is a weaker form of barrier() that affects only the specific
   load operation, while barrier() is a general compiler level memory barrier.
   READ_ONCE() was not available at the time when the barrier was added.

2) Aside of that READ_ONCE() is descriptive and self explainatory while a
   barrier without comment is not clear to the casual reader.

No functional change.

[ tglx: Massaged changelog ]

Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Cc: dave@stgolabs.net
Cc: peterz@infradead.org
Cc: linux@rasmusvillemoes.dk
Cc: akpm@linux-foundation.org
Cc: fengguang.wu@intel.com
Cc: bigeasy@linutronix.de
Link: http://lkml.kernel.org/r/1457314344-5685-1-git-send-email-nasa4836@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-03-08 17:04:02 +01:00
Mel Gorman 65d8fc777f futex: Remove requirement for lock_page() in get_futex_key()
When dealing with key handling for shared futexes, we can drastically reduce
the usage/need of the page lock. 1) For anonymous pages, the associated futex
object is the mm_struct which does not require the page lock. 2) For inode
based, keys, we can check under RCU read lock if the page mapping is still
valid and take reference to the inode. This just leaves one rare race that
requires the page lock in the slow path when examining the swapcache.

Additionally realtime users currently have a problem with the page lock being
contended for unbounded periods of time during futex operations.

Task A
     get_futex_key()
     lock_page()
    ---> preempted

Now any other task trying to lock that page will have to wait until
task A gets scheduled back in, which is an unbound time.

With this patch, we pretty much have a lockless futex_get_key().

Experiments show that this patch can boost/speedup the hashing of shared
futexes with the perf futex benchmarks (which is good for measuring such
change) by up to 45% when there are high (> 100) thread counts on a 60 core
Westmere. Lower counts are pretty much in the noise range or less than 10%,
but mid range can be seen at over 30% overall throughput (hash ops/sec).
This makes anon-mem shared futexes much closer to its private counterpart.

Signed-off-by: Mel Gorman <mgorman@suse.de>
[ Ported on top of thp refcount rework, changelog, comments, fixes. ]
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Mason <clm@fb.com>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: dave@stgolabs.net
Link: http://lkml.kernel.org/r/1455045314-8305-3-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-02-17 10:42:17 +01:00
Davidlohr Bueso 8ad7b378d0 futex: Rename barrier references in ordering guarantees
Ingo suggested we rename how we reference barriers A and B
regarding futex ordering guarantees. This patch replaces,
for both barriers, MB (A) with smp_mb(); (A), such that:

 - We explicitly state that the barriers are SMP, and

 - We standardize how we reference these across futex.c
   helping readers follow what barrier does what and where.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Mason <clm@fb.com>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: dave@stgolabs.net
Link: http://lkml.kernel.org/r/1455045314-8305-2-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-02-17 10:42:17 +01:00
Thomas Gleixner b4abf91047 rtmutex: Make wait_lock irq safe
Sasha reported a lockdep splat about a potential deadlock between RCU boosting
rtmutex and the posix timer it_lock.

CPU0					CPU1

rtmutex_lock(&rcu->rt_mutex)
  spin_lock(&rcu->rt_mutex.wait_lock)
					local_irq_disable()
					spin_lock(&timer->it_lock)
					spin_lock(&rcu->mutex.wait_lock)
--> Interrupt
    spin_lock(&timer->it_lock)

This is caused by the following code sequence on CPU1

     rcu_read_lock()
     x = lookup();
     if (x)
     	spin_lock_irqsave(&x->it_lock);
     rcu_read_unlock();
     return x;

We could fix that in the posix timer code by keeping rcu read locked across
the spinlocked and irq disabled section, but the above sequence is common and
there is no reason not to support it.

Taking rt_mutex.wait_lock irq safe prevents the deadlock.

Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
2016-01-26 11:08:35 +01:00
Jann Horn caaee6234d ptrace: use fsuid, fsgid, effective creds for fs access checks
By checking the effective credentials instead of the real UID / permitted
capabilities, ensure that the calling process actually intended to use its
credentials.

To ensure that all ptrace checks use the correct caller credentials (e.g.
in case out-of-tree code or newly added code omits the PTRACE_MODE_*CREDS
flag), use two new flags and require one of them to be set.

The problem was that when a privileged task had temporarily dropped its
privileges, e.g.  by calling setreuid(0, user_uid), with the intent to
perform following syscalls with the credentials of a user, it still passed
ptrace access checks that the user would not be able to pass.

While an attacker should not be able to convince the privileged task to
perform a ptrace() syscall, this is a problem because the ptrace access
check is reused for things in procfs.

In particular, the following somewhat interesting procfs entries only rely
on ptrace access checks:

 /proc/$pid/stat - uses the check for determining whether pointers
     should be visible, useful for bypassing ASLR
 /proc/$pid/maps - also useful for bypassing ASLR
 /proc/$pid/cwd - useful for gaining access to restricted
     directories that contain files with lax permissions, e.g. in
     this scenario:
     lrwxrwxrwx root root /proc/13020/cwd -> /root/foobar
     drwx------ root root /root
     drwxr-xr-x root root /root/foobar
     -rw-r--r-- root root /root/foobar/secret

Therefore, on a system where a root-owned mode 6755 binary changes its
effective credentials as described and then dumps a user-specified file,
this could be used by an attacker to reveal the memory layout of root's
processes or reveal the contents of files he is not allowed to access
(through /proc/$pid/cwd).

[akpm@linux-foundation.org: fix warning]
Signed-off-by: Jann Horn <jann@thejh.net>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Morris <james.l.morris@oracle.com>
Cc: "Serge E. Hallyn" <serge.hallyn@ubuntu.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-01-20 17:09:18 -08:00
Dominik Dingel 4a9e1cda27 mm: bring in additional flag for fixup_user_fault to signal unlock
During Jason's work with postcopy migration support for s390 a problem
regarding gmap faults was discovered.

The gmap code will call fixup_user_fault which will end up always in
handle_mm_fault.  Till now we never cared about retries, but as the
userfaultfd code kind of relies on it.  this needs some fix.

This patchset does not take care of the futex code.  I will now look
closer at this.

This patch (of 2):

With the introduction of userfaultfd, kvm on s390 needs fixup_user_fault
to pass in FAULT_FLAG_ALLOW_RETRY and give feedback if during the
faulting we ever unlocked mmap_sem.

This patch brings in the logic to handle retries as well as it cleans up
the current documentation.  fixup_user_fault was not having the same
semantics as filemap_fault.  It never indicated if a retry happened and
so a caller wasn't able to handle that case.  So we now changed the
behaviour to always retry a locked mmap_sem.

Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: "Jason J. Herne" <jjherne@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Eric B Munson <emunson@akamai.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Dominik Dingel <dingel@linux.vnet.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-01-15 17:56:32 -08:00
Kirill A. Shutemov 14d27abd1d futex, thp: remove special case for THP in get_futex_key
With new THP refcounting, we don't need tricks to stabilize huge page.
If we've got reference to tail page, it can't split under us.

This patch effectively reverts a5b338f2b0 ("thp: update futex compound
knowledge").

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Tested-by: Artem Savkov <artem.savkov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-01-15 17:56:32 -08:00
Darren Hart 337f13046f futex: Allow FUTEX_CLOCK_REALTIME with FUTEX_WAIT op
While reviewing Michael Kerrisk's recent futex manpage update, I noticed
that we allow the FUTEX_CLOCK_REALTIME flag for FUTEX_WAIT_BITSET but
not for FUTEX_WAIT.

FUTEX_WAIT is treated as a simple version for FUTEX_WAIT_BITSET
internally (with a bitmask of FUTEX_BITSET_MATCH_ANY). As such, I cannot
come up with a reason for this exclusion for FUTEX_WAIT.

This change does modify the behavior of the futex syscall, changing a
call with FUTEX_WAIT | FUTEX_CLOCK_REALTIME from returning -ENOSYS, to be
equivalent to FUTEX_WAIT_BITSET | FUTEX_CLOCK_REALTIME with a bitset of
FUTEX_BITSET_MATCH_ANY.

Reported-by: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Link: http://lkml.kernel.org/r/9f3bdc116d79d23f5ee72ceb9a2a857f5ff8fa29.1450474525.git.dvhart@linux.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-12-20 12:43:25 +01:00
Thomas Gleixner 885c2cb770 futex: Cleanup the goto confusion in requeue_pi()
out_unlock: does not only drop the locks, it also drops the refcount
on the pi_state. Really intuitive.

Move the label after the put_pi_state() call and use 'break' in the
error handling path of the requeue loop.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <darren@dvhart.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Bhuvanesh_Surachari@mentor.com
Cc: Andy Lowe <Andy_Lowe@mentor.com>
Link: http://lkml.kernel.org/r/20151219200607.526665141@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-12-20 12:43:25 +01:00
Thomas Gleixner 4959f2de11 futex: Remove pointless put_pi_state calls in requeue()
In the error handling cases we neither have pi_state nor a reference
to it. Remove the pointless code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <darren@dvhart.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Bhuvanesh_Surachari@mentor.com
Cc: Andy Lowe <Andy_Lowe@mentor.com>
Link: http://lkml.kernel.org/r/20151219200607.432780944@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-12-20 12:43:25 +01:00
Thomas Gleixner ecb38b78f6 futex: Document pi_state refcounting in requeue code
Documentation of the pi_state refcounting in the requeue code is non
existent. Add it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <darren@dvhart.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Bhuvanesh_Surachari@mentor.com
Cc: Andy Lowe <Andy_Lowe@mentor.com>
Link: http://lkml.kernel.org/r/20151219200607.335938312@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-12-20 12:43:24 +01:00
Thomas Gleixner 29e9ee5d48 futex: Rename free_pi_state() to put_pi_state()
free_pi_state() is confusing as it is in fact only freeing/caching the
pi state when the last reference is gone. Rename it to put_pi_state()
which reflects better what it is doing.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <darren@dvhart.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Bhuvanesh_Surachari@mentor.com
Cc: Andy Lowe <Andy_Lowe@mentor.com>
Link: http://lkml.kernel.org/r/20151219200607.259636467@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-12-20 12:43:24 +01:00
Thomas Gleixner fb75a4282d futex: Drop refcount if requeue_pi() acquired the rtmutex
If the proxy lock in the requeue loop acquires the rtmutex for a
waiter then it acquired also refcount on the pi_state related to the
futex, but the waiter side does not drop the reference count.

Add the missing free_pi_state() call.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <darren@dvhart.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Bhuvanesh_Surachari@mentor.com
Cc: Andy Lowe <Andy_Lowe@mentor.com>
Link: http://lkml.kernel.org/r/20151219200607.178132067@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
2015-12-20 12:43:24 +01:00
Linus Torvalds e880e87488 driver core update for 4.4-rc1
Here's the "big" driver core updates for 4.4-rc1.  Primarily a bunch of
 debugfs updates, with a smattering of minor driver core fixes and
 updates as well.
 
 All have been in linux-next for a long time.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'driver-core-4.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core updates from Greg KH:
 "Here's the "big" driver core updates for 4.4-rc1.  Primarily a bunch
  of debugfs updates, with a smattering of minor driver core fixes and
  updates as well.

  All have been in linux-next for a long time"

* tag 'driver-core-4.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  debugfs: Add debugfs_create_ulong()
  of: to support binding numa node to specified device in devicetree
  debugfs: Add read-only/write-only bool file ops
  debugfs: Add read-only/write-only size_t file ops
  debugfs: Add read-only/write-only x64 file ops
  debugfs: Consolidate file mode checks in debugfs_create_*()
  Revert "mm: Check if section present during memory block (un)registering"
  driver-core: platform: Provide helpers for multi-driver modules
  mm: Check if section present during memory block (un)registering
  devres: fix a for loop bounds check
  CMA: fix CONFIG_CMA_SIZE_MBYTES overflow in 64bit
  base/platform: assert that dev_pm_domain callbacks are called unconditionally
  sysfs: correctly handle short reads on PREALLOC attrs.
  base: soc: siplify ida usage
  kobject: move EXPORT_SYMBOL() macros next to corresponding definitions
  kobject: explain what kobject's sd field is
  debugfs: document that debugfs_remove*() accepts NULL and error values
  debugfs: Pass bool pointer to debugfs_create_bool()
  ACPI / EC: Fix broken 64bit big-endian users of 'global_lock'
2015-11-04 21:50:37 -08:00
Viresh Kumar 621a5f7ad9 debugfs: Pass bool pointer to debugfs_create_bool()
Its a bit odd that debugfs_create_bool() takes 'u32 *' as an argument,
when all it needs is a boolean pointer.

It would be better to update this API to make it accept 'bool *'
instead, as that will make it more consistent and often more convenient.
Over that bool takes just a byte.

That required updates to all user sites as well, in the same commit
updating the API. regmap core was also using
debugfs_{read|write}_file_bool(), directly and variable types were
updated for that to be bool as well.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-04 11:36:07 +01:00
Rasmus Villemoes ac742d3718 futex: Force hot variables into a single cache line
futex_hash() references two global variables: the base pointer
futex_queues and the size of the array futex_hashsize. The latter is
marked __read_mostly, while the former is not, so they are likely to
end up very far from each other. This means that futex_hash() is
likely to encounter two cache misses.

We could mark futex_queues as __read_mostly as well, but that doesn't
guarantee they'll end up next to each other (and even if they do, they
may still end up in different cache lines). So put the two variables
in a small singleton struct with sufficient alignment and mark that as
__read_mostly.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: kbuild test robot <fengguang.wu@intel.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: http://lkml.kernel.org/r/1441834601-13633-1-git-send-email-linux@rasmusvillemoes.dk
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-09-22 16:23:15 +02:00
kbuild test robot 5d285a7f35 futex: Make should_fail_futex() static
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: kbuild-all@01.org
Cc: tipbuild@zytor.com
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <darren@dvhart.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Brian Silverman <bsilver16384@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-07-20 21:43:54 +02:00
Davidlohr Bueso ab51fbab39 futex: Fault/error injection capabilities
Although futexes are well known for being a royal pita,
we really have very little debugging capabilities - except
for relying on tglx's eye half the time.

By simply making use of the existing fault-injection machinery,
we can improve this situation, allowing generating artificial
uaddress faults and deadlock scenarios. Of course, when this is
disabled in production systems, the overhead for failure checks
is practically zero -- so this is very cheap at the same time.
Future work would be nice to now enhance trinity to make use of
this.

There is a special tunable 'ignore-private', which can filter
out private futexes. Given the tsk->make_it_fail filter and
this option, pi futexes can be narrowed down pretty closely.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <darren@dvhart.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Link: http://lkml.kernel.org/r/1435645562-975-3-git-send-email-dave@stgolabs.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-07-20 11:45:45 +02:00
Davidlohr Bueso 767f509ca1 futex: Enhance comments in futex_lock_pi() for blocking paths
... serves a bit better to clarify between blocking
and non-blocking code paths.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <darren@dvhart.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Link: http://lkml.kernel.org/r/1435645562-975-2-git-send-email-dave@stgolabs.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-07-20 11:45:45 +02:00
Linus Torvalds a262948335 Merge branch 'sched-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Thomas Gleixner:
 "These locking updates depend on the alreay merged sched/core branch:

   - Lockless top waiter wakeup for rtmutex (Davidlohr)

   - Reduce hash bucket lock contention for PI futexes (Sebastian)

   - Documentation update (Davidlohr)"

* 'sched-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/rtmutex: Update stale plist comments
  futex: Lower the lock contention on the HB lock during wake up
  locking/rtmutex: Implement lockless top-waiter wakeup
2015-06-24 14:46:01 -07:00
Linus Torvalds 43224b96af Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
 "A rather largish update for everything time and timer related:

   - Cache footprint optimizations for both hrtimers and timer wheel

   - Lower the NOHZ impact on systems which have NOHZ or timer migration
     disabled at runtime.

   - Optimize run time overhead of hrtimer interrupt by making the clock
     offset updates smarter

   - hrtimer cleanups and removal of restrictions to tackle some
     problems in sched/perf

   - Some more leap second tweaks

   - Another round of changes addressing the 2038 problem

   - First step to change the internals of clock event devices by
     introducing the necessary infrastructure

   - Allow constant folding for usecs/msecs_to_jiffies()

   - The usual pile of clockevent/clocksource driver updates

  The hrtimer changes contain updates to sched, perf and x86 as they
  depend on them plus changes all over the tree to cleanup API changes
  and redundant code, which got copied all over the place.  The y2038
  changes touch s390 to remove the last non 2038 safe code related to
  boot/persistant clock"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (114 commits)
  clocksource: Increase dependencies of timer-stm32 to limit build wreckage
  timer: Minimize nohz off overhead
  timer: Reduce timer migration overhead if disabled
  timer: Stats: Simplify the flags handling
  timer: Replace timer base by a cpu index
  timer: Use hlist for the timer wheel hash buckets
  timer: Remove FIFO "guarantee"
  timers: Sanitize catchup_timer_jiffies() usage
  hrtimer: Allow hrtimer::function() to free the timer
  seqcount: Introduce raw_write_seqcount_barrier()
  seqcount: Rename write_seqcount_barrier()
  hrtimer: Fix hrtimer_is_queued() hole
  hrtimer: Remove HRTIMER_STATE_MIGRATE
  selftest: Timers: Avoid signal deadlock in leap-a-day
  timekeeping: Copy the shadow-timekeeper over the real timekeeper last
  clockevents: Check state instead of mode in suspend/resume path
  selftests: timers: Add leap-second timer edge testing to leap-a-day.c
  ntp: Do leapsecond adjustment in adjtimex read path
  time: Prevent early expiry of hrtimers[CLOCK_REALTIME] at the leap second edge
  ntp: Introduce and use SECS_PER_DAY macro instead of 86400
  ...
2015-06-22 18:57:44 -07:00
Linus Torvalds 23b7776290 Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
 "The main changes are:

   - lockless wakeup support for futexes and IPC message queues
     (Davidlohr Bueso, Peter Zijlstra)

   - Replace spinlocks with atomics in thread_group_cputimer(), to
     improve scalability (Jason Low)

   - NUMA balancing improvements (Rik van Riel)

   - SCHED_DEADLINE improvements (Wanpeng Li)

   - clean up and reorganize preemption helpers (Frederic Weisbecker)

   - decouple page fault disabling machinery from the preemption
     counter, to improve debuggability and robustness (David
     Hildenbrand)

   - SCHED_DEADLINE documentation updates (Luca Abeni)

   - topology CPU masks cleanups (Bartosz Golaszewski)

   - /proc/sched_debug improvements (Srikar Dronamraju)"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (79 commits)
  sched/deadline: Remove needless parameter in dl_runtime_exceeded()
  sched: Remove superfluous resetting of the p->dl_throttled flag
  sched/deadline: Drop duplicate init_sched_dl_class() declaration
  sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target
  sched/deadline: Make init_sched_dl_class() __init
  sched/deadline: Optimize pull_dl_task()
  sched/preempt: Add static_key() to preempt_notifiers
  sched/preempt: Fix preempt notifiers documentation about hlist_del() within unsafe iteration
  sched/stop_machine: Fix deadlock between multiple stop_two_cpus()
  sched/debug: Add sum_sleep_runtime to /proc/<pid>/sched
  sched/debug: Replace vruntime with wait_sum in /proc/sched_debug
  sched/debug: Properly format runnable tasks in /proc/sched_debug
  sched/numa: Only consider less busy nodes as numa balancing destinations
  Revert 095bebf61a ("sched/numa: Do not move past the balance point if unbalanced")
  sched/fair: Prevent throttling in early pick_next_task_fair()
  preempt: Reorganize the notrace definitions a bit
  preempt: Use preempt_schedule_context() as the official tracing preemption point
  sched: Make preempt_schedule_context() function-tracing safe
  x86: Remove cpu_sibling_mask() and cpu_core_mask()
  x86: Replace cpu_**_mask() with topology_**_cpumask()
  ...
2015-06-22 15:52:04 -07:00
Sebastian Andrzej Siewior 802ab58da7 futex: Lower the lock contention on the HB lock during wake up
wake_futex_pi() wakes the task before releasing the hash bucket lock
(HB). The first thing the woken up task usually does is to acquire the
lock which requires the HB lock. On SMP Systems this leads to blocking
on the HB lock which is released by the owner shortly after.
This patch rearranges the unlock path by first releasing the HB lock and
then waking up the task.

[ tglx: Fixed up the rtmutex unlock path ]

Originally-from: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Link: http://lkml.kernel.org/r/20150617083350.GA2433@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-06-19 21:26:38 +02:00
Peter Zijlstra b92b8b35a2 locking/arch: Rename set_mb() to smp_store_mb()
Since set_mb() is really about an smp_mb() -- not a IO/DMA barrier
like mb() rename it to match the recent smp_load_acquire() and
smp_store_release().

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-05-19 08:32:00 +02:00
Davidlohr Bueso 1d0dcb3ad9 futex: Implement lockless wakeups
Given the overall futex architecture, any chance of reducing
hb->lock contention is welcome. In this particular case, using
wake-queues to enable lockless wakeups addresses very much real
world performance concerns, even cases of soft-lockups in cases
of large amounts of blocked tasks (which is not hard to find in
large boxes, using but just a handful of futex).

At the lowest level, this patch can reduce latency of a single thread
attempting to acquire hb->lock in highly contended scenarios by a
up to 2x. At lower counts of nr_wake there are no regressions,
confirming, of course, that the wake_q handling overhead is practically
non existent. For instance, while a fair amount of variation,
the extended pef-bench wakeup benchmark shows for a 20 core machine
the following avg per-thread time to wakeup its share of tasks:

	nr_thr	ms-before	ms-after
	16 	0.0590		0.0215
	32 	0.0396		0.0220
	48 	0.0417		0.0182
	64 	0.0536		0.0236
	80 	0.0414		0.0097
	96 	0.0672		0.0152

Naturally, this can cause spurious wakeups. However there is no core code
that cannot handle them afaict, and furthermore tglx does have the point
that other events can already trigger them anyway.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Mason <clm@fb.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: George Spelvin <linux@horizon.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1430494072-30283-3-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-05-08 12:21:40 +02:00
Thomas Gleixner 2e4b0d3fe8 futex: Remove bogus hrtimer_active() check
The check for hrtimer_active() after starting the timer is
pointless. If the timer is inactive it has expired already and
therefor the task pointer is already NULL.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20150414203502.985825453@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-04-22 17:06:51 +02:00
Ingo Molnar 2ae7902681 Linux 34.0-rc1
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Merge tag 'v4.0-rc1' into locking/core, to refresh the tree before merging new changes

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-24 08:41:07 +01:00
Oleg Nesterov a212946446 locking/futex: Check PF_KTHREAD rather than !p->mm to filter out kthreads
attach_to_pi_owner() checks p->mm to prevent attaching to kthreads and
this looks doubly wrong:

1. It should actually check PF_KTHREAD, kthread can do use_mm().

2. If this task is not kthread and it is actually the lock owner we can
   wrongly return -EPERM instead of -ESRCH or retry-if-EAGAIN.

   And note that this wrong EPERM is the likely case unless the exiting
   task is (auto)reaped quickly, we check ->mm before PF_EXITING.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Darren Hart <darren@dvhart.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mateusz Guzik <mguzik@redhat.com>
Link: http://lkml.kernel.org/r/20150202140536.GA26406@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-18 16:57:09 +01:00
Andy Lutomirski f56141e3e2 all arches, signal: move restart_block to struct task_struct
If an attacker can cause a controlled kernel stack overflow, overwriting
the restart block is a very juicy exploit target.  This is because the
restart_block is held in the same memory allocation as the kernel stack.

Moving the restart block to struct task_struct prevents this exploit by
making the restart_block harder to locate.

Note that there are other fields in thread_info that are also easy
targets, at least on some architectures.

It's also a decent simplification, since the restart code is more or less
identical on all architectures.

[james.hogan@imgtec.com: metag: align thread_info::supervisor_stack]
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: David Miller <davem@davemloft.net>
Acked-by: Richard Weinberger <richard@nod.at>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Haavard Skinnemoen <hskinnemoen@gmail.com>
Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Cc: Steven Miao <realmz6@gmail.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Aurelien Jacquiot <a-jacquiot@ti.com>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Tested-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Chen Liqin <liqin.linux@gmail.com>
Cc: Lennox Wu <lennox.wu@gmail.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-12 18:54:12 -08:00
Michael Kerrisk 996636ddae futex: Fix argument handling in futex_lock_pi() calls
This patch fixes two separate buglets in calls to futex_lock_pi():

  * Eliminate unused 'detect' argument
  * Change unused 'timeout' argument of FUTEX_TRYLOCK_PI to NULL

The 'detect' argument of futex_lock_pi() seems never to have been
used (when it was included with the initial PI mutex implementation
in Linux 2.6.18, all checks against its value were disabled by
ANDing against 0 (i.e., if (detect... && 0)), and with
commit 778e9a9c3e, any mention of
this argument in futex_lock_pi() went way altogether. Its presence
now serves only to confuse readers of the code, by giving the
impression that the futex() FUTEX_LOCK_PI operation actually does
use the 'val' argument. This patch removes the argument.

The futex_lock_pi() call that corresponds to FUTEX_TRYLOCK_PI includes
'timeout' as one of its arguments. This misleads the reader into thinking
that the FUTEX_TRYLOCK_PI operation does employ timeouts for some sensible
purpose; but it does not.  Indeed, it cannot, because the checks at the
start of sys_futex() exclude FUTEX_TRYLOCK_PI from the set of operations
that do copy_from_user() on the timeout argument. So, in the
FUTEX_TRYLOCK_PI futex_lock_pi() call it would be simplest to change
'timeout' to 'NULL'. This patch does that.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: Darren Hart <darren@dvhart.com>
Link: http://lkml.kernel.org/r/54B96646.8010200@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-01-19 12:05:32 +01:00
Brian Silverman 30a6b8031f futex: Fix a race condition between REQUEUE_PI and task death
free_pi_state and exit_pi_state_list both clean up futex_pi_state's.
exit_pi_state_list takes the hb lock first, and most callers of
free_pi_state do too. requeue_pi doesn't, which means free_pi_state
can free the pi_state out from under exit_pi_state_list. For example:

task A                            |  task B
exit_pi_state_list                |
  pi_state =                      |
      curr->pi_state_list->next   |
                                  |  futex_requeue(requeue_pi=1)
                                  |    // pi_state is the same as
                                  |    // the one in task A
                                  |    free_pi_state(pi_state)
                                  |      list_del_init(&pi_state->list)
                                  |      kfree(pi_state)
  list_del_init(&pi_state->list)  |

Move the free_pi_state calls in requeue_pi to before it drops the hb
locks which it's already holding.

[ tglx: Removed a pointless free_pi_state() call and the hb->lock held
  	debugging. The latter comes via a seperate patch ]

Signed-off-by: Brian Silverman <bsilver16384@gmail.com>
Cc: austin.linux@gmail.com
Cc: darren@dvhart.com
Cc: peterz@infradead.org
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1414282837-23092-1-git-send-email-bsilver16384@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-10-26 16:16:18 +01:00
Davidlohr Bueso 993b2ff221 futex: Mention key referencing differences between shared and private futexes
Update our documentation as of fix 76835b0ebf (futex: Ensure
get_futex_key_refs() always implies a barrier). Explicitly
state that we don't do key referencing for private futexes.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Matteo Franchin <Matteo.Franchin@arm.com>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: http://lkml.kernel.org/r/1414121220.817.0.camel@linux-t7sj.site
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-10-26 16:16:18 +01:00
Catalin Marinas 76835b0ebf futex: Ensure get_futex_key_refs() always implies a barrier
Commit b0c29f79ec (futexes: Avoid taking the hb->lock if there's
nothing to wake up) changes the futex code to avoid taking a lock when
there are no waiters. This code has been subsequently fixed in commit
11d4616bd0 (futex: revert back to the explicit waiter counting code).
Both the original commit and the fix-up rely on get_futex_key_refs() to
always imply a barrier.

However, for private futexes, none of the cases in the switch statement
of get_futex_key_refs() would be hit and the function completes without
a memory barrier as required before checking the "waiters" in
futex_wake() -> hb_waiters_pending(). The consequence is a race with a
thread waiting on a futex on another CPU, allowing the waker thread to
read "waiters == 0" while the waiter thread to have read "futex_val ==
locked" (in kernel).

Without this fix, the problem (user space deadlocks) can be seen with
Android bionic's mutex implementation on an arm64 multi-cluster system.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Matteo Franchin <Matteo.Franchin@arm.com>
Fixes: b0c29f79ec (futexes: Avoid taking the hb->lock if there's nothing to wake up)
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Tested-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: <stable@vger.kernel.org>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-10-18 09:28:51 -07:00
Thomas Gleixner 13c42c2f43 futex: Unlock hb->lock in futex_wait_requeue_pi() error path
futex_wait_requeue_pi() calls futex_wait_setup(). If
futex_wait_setup() succeeds it returns with hb->lock held and
preemption disabled. Now the sanity check after this does:

        if (match_futex(&q.key, &key2)) {
	   	ret = -EINVAL;
		goto out_put_keys;
	}

which releases the keys but does not release hb->lock.

So we happily return to user space with hb->lock held and therefor
preemption disabled.

Unlock hb->lock before taking the exit route.

Reported-by: Dave "Trinity" Jones <davej@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Darren Hart <dvhart@linux.intel.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1409112318500.4178@nanos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-09-12 22:04:36 +02:00
Thomas Gleixner af54d6a1c3 futex: Simplify futex_lock_pi_atomic() and make it more robust
futex_lock_pi_atomic() is a maze of retry hoops and loops.

Reduce it to simple and understandable states:

First step is to lookup existing waiters (state) in the kernel.

If there is an existing waiter, validate it and attach to it.

If there is no existing waiter, check the user space value

If the TID encoded in the user space value is 0, take over the futex
preserving the owner died bit.

If the TID encoded in the user space value is != 0, lookup the owner
task, validate it and attach to it.

Reduces text size by 128 bytes on x8664.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Kees Cook <kees@outflux.net>
Cc: wad@chromium.org
Cc: Darren Hart <darren@dvhart.com>
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1406131137020.5170@nanos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-06-21 22:26:24 +02:00
Thomas Gleixner 04e1b2e52b futex: Split out the first waiter attachment from lookup_pi_state()
We want to be a bit more clever in futex_lock_pi_atomic() and separate
the possible states. Split out the code which attaches the first
waiter to the owner into a separate function. No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Darren Hart <darren@dvhart.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Kees Cook <kees@outflux.net>
Cc: wad@chromium.org
Link: http://lkml.kernel.org/r/20140611204237.271300614@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-06-21 22:26:23 +02:00
Thomas Gleixner e60cbc5cea futex: Split out the waiter check from lookup_pi_state()
We want to be a bit more clever in futex_lock_pi_atomic() and separate
the possible states. Split out the waiter verification into a separate
function. No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Darren Hart <darren@dvhart.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Kees Cook <kees@outflux.net>
Cc: wad@chromium.org
Link: http://lkml.kernel.org/r/20140611204237.180458410@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-06-21 22:26:23 +02:00
Thomas Gleixner bd1dbcc67c futex: Use futex_top_waiter() in lookup_pi_state()
No point in open coding the same function again.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Darren Hart <darren@dvhart.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Kees Cook <kees@outflux.net>
Cc: wad@chromium.org
Link: http://lkml.kernel.org/r/20140611204237.092947239@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-06-21 22:26:23 +02:00