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 <lukas.bulwahn@xxxxxxxxx>
---
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
