linux-kernel - [GIT PULL] percpu fix for v4.10-rc6

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Date:   Tue, 31 Jan 2017 11:55:37 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, dougmill@...ux.vnet.ibm.com
Subject: [GIT PULL] percpu fix for v4.10-rc6

Hello,

Douglas found and fixed a ref leak bug in percpu_ref_tryget[_live]().
The bug is caused by storing the return value of
atomic_long_inc_not_zero() into an int temp variable before returning
it as a bool.  The interim cast to int loses the upper bits and can
lead to false negatives.  As percpu_ref uses a high bit to mark a
draining counter, this can happen relatively easily.  Fixed by using
bool for the temp variable.

Thanks.

The following changes since commit 1b1bc42c1692e9b62756323c675a44cb1a1f9dbd:

  Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net (2017-01-27 12:54:16 -0800)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu.git for-4.10-fixes

for you to fetch changes up to 966d2b04e070bc040319aaebfec09e0144dc3341:

  percpu-refcount: fix reference leak during percpu-atomic transition (2017-01-28 07:49:42 -0500)

----------------------------------------------------------------
Douglas Miller (1):
      percpu-refcount: fix reference leak during percpu-atomic transition

 include/linux/percpu-refcount.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index 1c7eec0..3a481a4 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -204,7 +204,7 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
 static inline bool percpu_ref_tryget(struct percpu_ref *ref)
 {
 	unsigned long __percpu *percpu_count;
-	int ret;
+	bool ret;
 
 	rcu_read_lock_sched();
 
@@ -238,7 +238,7 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
 static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
 {
 	unsigned long __percpu *percpu_count;
-	int ret = false;
+	bool ret = false;
 
 	rcu_read_lock_sched();
 

-- 
tejun