From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Layton Subject: [PATCH 01/10] locks: close potential race in lease_get_mtime Date: Sat, 23 Aug 2014 10:41:09 -0400 Message-ID: <1408804878-1331-2-git-send-email-jlayton@primarydata.com> References: <1408804878-1331-1-git-send-email-jlayton@primarydata.com> Cc: bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org, hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, cluster-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Return-path: In-Reply-To: <1408804878-1331-1-git-send-email-jlayton-7I+n7zu2hftEKMMhf/gKZA@public.gmane.org> Sender: linux-cifs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org lease_get_mtime is called without the i_lock held, so there's no guarantee about the stability of the list. Between the time when we assign "flock" and then dereference it to check whether it's a lease and for write, the lease could be freed. Ensure that that doesn't occur by taking the i_lock before trying to check the lease. Cc: J. Bruce Fields Signed-off-by: Jeff Layton --- fs/locks.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/fs/locks.c b/fs/locks.c index d7e15a256f8f..58ce8897f2e4 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -1456,8 +1456,18 @@ EXPORT_SYMBOL(__break_lease); */ void lease_get_mtime(struct inode *inode, struct timespec *time) { - struct file_lock *flock = inode->i_flock; - if (flock && IS_LEASE(flock) && (flock->fl_type == F_WRLCK)) + bool has_lease = false; + struct file_lock *flock; + + if (inode->i_flock) { + spin_lock(&inode->i_lock); + flock = inode->i_flock; + if (flock && IS_LEASE(flock) && (flock->fl_type == F_WRLCK)) + has_lease = true; + spin_unlock(&inode->i_lock); + } + + if (has_lease) *time = current_fs_time(inode->i_sb); else *time = inode->i_mtime; -- 1.9.3