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

Pull locking updates from Ingo Molnar:
 "The main changes in this cycle were:

   - Add CONFIG_REFCOUNT_FULL=y to allow the disabling of the 'full'
     (robustness checked) refcount_t implementation with slightly lower
     runtime overhead. (Kees Cook)

     The lighter weight variant is the default. The two variants use the
     same API. Having this variant was a precondition by some
     maintainers to merge refcount_t cleanups.

   - Add lockdep support for rtmutexes (Peter Zijlstra)

   - liblockdep fixes and improvements (Sasha Levin, Ben Hutchings)

   - ... misc fixes and improvements"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (30 commits)
  locking/refcount: Remove the half-implemented refcount_sub() API
  locking/refcount: Create unchecked atomic_t implementation
  locking/rtmutex: Don't initialize lockdep when not required
  locking/selftest: Add RT-mutex support
  locking/selftest: Remove the bad unlock ordering test
  rt_mutex: Add lockdep annotations
  MAINTAINERS: Claim atomic*_t maintainership
  locking/x86: Remove the unused atomic_inc_short() methd
  tools/lib/lockdep: Remove private kernel headers
  tools/lib/lockdep: Hide liblockdep output from test results
  tools/lib/lockdep: Add dummy current_gfp_context()
  tools/include: Add IS_ERR_OR_NULL to err.h
  tools/lib/lockdep: Add empty __is_[module,kernel]_percpu_address
  tools/lib/lockdep: Include err.h
  tools/include: Add (mostly) empty include/linux/sched/mm.h
  tools/lib/lockdep: Use LDFLAGS
  tools/lib/lockdep: Remove double-quotes from soname
  tools/lib/lockdep: Fix object file paths used in an out-of-tree build
  tools/lib/lockdep: Fix compilation for 4.11
  tools/lib/lockdep: Don't mix fd-based and stream IO
  ...

3 files changed, 10 insertions, 15 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 6c00e5b00f8b..f76b214cf7ad 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -867,4 +867,13 @@ config STRICT_MODULE_RWX
 config ARCH_WANT_RELAX_ORDER
 	bool
 
+config REFCOUNT_FULL
+	bool "Perform full reference count validation at the expense of speed"
+	help
+	  Enabling this switches the refcounting infrastructure from a fast
+	  unchecked atomic_t implementation to a fully state checked
+	  implementation, which can be (slightly) slower but provides protections
+	  against various use-after-free conditions that can be used in
+	  security flaw exploits.
+
 source "kernel/gcov/Kconfig"
diff --git a/arch/tile/lib/atomic_asm_32.S b/arch/tile/lib/atomic_asm_32.S
index 1a70e6c0f259..94709ab41ed8 100644
--- a/arch/tile/lib/atomic_asm_32.S
+++ b/arch/tile/lib/atomic_asm_32.S
@@ -24,8 +24,7 @@
  * has an opportunity to return -EFAULT to the user if needed.
  * The 64-bit routines just return a "long long" with the value,
  * since they are only used from kernel space and don't expect to fault.
- * Support for 16-bit ops is included in the framework but we don't provide
- * any (x86_64 has an atomic_inc_short(), so we might want to some day).
+ * Support for 16-bit ops is included in the framework but we don't provide any.
  *
  * Note that the caller is advised to issue a suitable L1 or L2
  * prefetch on the address being manipulated to avoid extra stalls.
diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h
index caa5798c92f4..33380b871463 100644
--- a/arch/x86/include/asm/atomic.h
+++ b/arch/x86/include/asm/atomic.h
@@ -246,19 +246,6 @@ static __always_inline int __atomic_add_unless(atomic_t *v, int a, int u)
 	return c;
 }
 
-/**
- * atomic_inc_short - increment of a short integer
- * @v: pointer to type int
- *
- * Atomically adds 1 to @v
- * Returns the new value of @u
- */
-static __always_inline short int atomic_inc_short(short int *v)
-{
-	asm(LOCK_PREFIX "addw $1, %0" : "+m" (*v));
-	return *v;
-}
-
 #ifdef CONFIG_X86_32
 # include <asm/atomic64_32.h>
 #else