From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lukas Bulwahn Subject: [PATCH] md: properly lock and unlock in rdev_attr_store() Date: Sun, 28 Apr 2019 12:40:41 +0200 Message-ID: <20190428104041.11262-1-lukas.bulwahn@gmail.com> Return-path: Sender: linux-kernel-owner@vger.kernel.org To: Shaohua Li , Neil Brown , Arnd Bergmann , Himanshu Jha Cc: clang-built-linux@googlegroups.com, linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, Lukas Bulwahn List-Id: linux-raid.ids rdev_attr_store() should lock and unlock mddev->reconfig_mutex in a balanced way with mddev_lock() and mddev_unlock(). But when rdev->mddev is NULL, rdev_attr_store() would try to unlock without locking before. Resolve this locking issue.. This locking issue was detected with Clang Thread Safety Analyser: drivers/md/md.c:3393:3: warning: releasing mutex 'mddev->reconfig_mutex' that was not held [-Wthread-safety-analysis] mddev_unlock(mddev); ^ This warning was reported after annotating mutex functions and mddev_lock() and mddev_unlock(). Fixes: 27c529bb8e90 ("md: lock access to rdev attributes properly") Link: https://groups.google.com/d/topic/clang-built-linux/CvBiiQLB0H4/discussion Signed-off-by: Lukas Bulwahn --- Arnd, Neil, here a proposal to fix lock and unlocking asymmetry. I quite sure that if mddev is NULL, it should just return. I am still puzzled if the return value from mddev_lock() should be really return by rdev_attr_store() when it is not 0. But that was the behaviour before, so I will keep it that way. drivers/md/md.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 05ffffb8b769..a9735d8f1e70 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -3384,7 +3384,9 @@ rdev_attr_store(struct kobject *kobj, struct attribute *attr, return -EIO; if (!capable(CAP_SYS_ADMIN)) return -EACCES; - rv = mddev ? mddev_lock(mddev): -EBUSY; + if (!mddev) + return -EBUSY; + rv = mddev_lock(mddev); if (!rv) { if (rdev->mddev == NULL) rv = -EBUSY; -- 2.17.1