From 962bd40bc30e412828e091bfda041b7547e779c8 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Tue, 10 Jun 2014 12:24:40 -0400 Subject: [PATCH] locks: add missing memory barrier in break_deleg break_deleg is subject to the same potential race as break_lease. Add a memory barrier to prevent it. Signed-off-by: Jeff Layton --- include/linux/fs.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/include/linux/fs.h b/include/linux/fs.h index c3f46e499dd0..22ae79650b82 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1914,6 +1914,12 @@ static inline int break_lease(struct inode *inode, unsigned int mode) static inline int break_deleg(struct inode *inode, unsigned int mode) { + /* + * Since this check is lockless, we must ensure that any refcounts + * taken are done before checking inode->i_flock. Otherwise, we could + * end up racing with tasks trying to set a new lease on this file. + */ + smp_mb(); if (inode->i_flock) return __break_lease(inode, mode, FL_DELEG); return 0;