linux-toradex.git/kernel/futex.c, branch v4.4.8

futex: Drop refcount if requeue_pi() acquired the rtmutex

2016-02-25T20:01:23+00:00

commit fb75a4282d0d9a3c7c44d940582c2d226cf3acfb upstream.

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 
Cc: Peter Zijlstra 
Cc: Darren Hart 
Cc: Davidlohr Bueso 
Cc: Bhuvanesh_Surachari@mentor.com
Cc: Andy Lowe 
Link: http://lkml.kernel.org/r/20151219200607.178132067@linutronix.de
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

ptrace: use fsuid, fsgid, effective creds for fs access checks

2016-02-25T20:01:16+00:00

commit caaee6234d05a58c5b4d05e7bf766131b810a657 upstream.

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 
Acked-by: Kees Cook 
Cc: Casey Schaufler 
Cc: Oleg Nesterov 
Cc: Ingo Molnar 
Cc: James Morris 
Cc: "Serge E. Hallyn" 
Cc: Andy Shevchenko 
Cc: Andy Lutomirski 
Cc: Al Viro 
Cc: "Eric W. Biederman" 
Cc: Willy Tarreau 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

Merge tag 'driver-core-4.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

2015-11-05T05:50:37+00:00

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'

debugfs: Pass bool pointer to debugfs_create_bool()

2015-10-04T10:36:07+00:00

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 
Acked-by: Mark Brown 
Acked-by: Charles Keepax 
Signed-off-by: Greg Kroah-Hartman

futex: Force hot variables into a single cache line

2015-09-22T14:23:15+00:00

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 
Cc: Peter Zijlstra 
Cc: Davidlohr Bueso 
Cc: kbuild test robot 
Cc: Sebastian Andrzej Siewior 
Link: http://lkml.kernel.org/r/1441834601-13633-1-git-send-email-linux@rasmusvillemoes.dk
Signed-off-by: Thomas Gleixner

futex: Make should_fail_futex() static

2015-07-20T19:43:54+00:00

Signed-off-by: Fengguang Wu 
Cc: kbuild-all@01.org
Cc: tipbuild@zytor.com
Cc: Davidlohr Bueso 
Cc: Peter Zijlstra 
Cc: Darren Hart 
Cc: Oleg Nesterov 
Cc: Brian Silverman 
Cc: Andy Lutomirski 
Cc: Sebastian Andrzej Siewior 
Signed-off-by: Thomas Gleixner

futex: Fault/error injection capabilities

2015-07-20T09:45:45+00:00

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 
Cc: Peter Zijlstra 
Cc: Darren Hart 
Cc: Davidlohr Bueso 
Link: http://lkml.kernel.org/r/1435645562-975-3-git-send-email-dave@stgolabs.net
Signed-off-by: Thomas Gleixner

futex: Enhance comments in futex_lock_pi() for blocking paths

2015-07-20T09:45:45+00:00

... serves a bit better to clarify between blocking
and non-blocking code paths.

Signed-off-by: Davidlohr Bueso 
Cc: Peter Zijlstra 
Cc: Darren Hart 
Cc: Davidlohr Bueso 
Link: http://lkml.kernel.org/r/1435645562-975-2-git-send-email-dave@stgolabs.net
Signed-off-by: Thomas Gleixner

Merge branch 'sched-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2015-06-24T21:46:01+00:00

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

Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2015-06-23T01:57:44+00:00

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
  ...