[PATCH v4 05/11] md/raid5-cache: Take mddev_lock in r5c_journal_mode_show()

[Logan Gunthorpe <logang@deltatee.com>]

The mddev->lock spinlock doesn't protect against the removal of
conf->log in r5l_exit_log() so conf->log may be freed before it
is used.

To fix this, take the mddev_lock() insteaad of the mddev->lock spinlock.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/raid5-cache.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 83c184eddbda..ca8fc317da95 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -2534,12 +2534,13 @@ static ssize_t r5c_journal_mode_show(struct mddev *mddev, char *page)
 	struct r5conf *conf;
 	int ret;
 
-	spin_lock(&mddev->lock);
+	ret = mddev_lock(mddev);
+	if (ret)
+		return ret;
+
 	conf = mddev->private;
-	if (!conf || !conf->log) {
-		spin_unlock(&mddev->lock);
-		return 0;
-	}
+	if (!conf || !conf->log)
+		goto out_unlock;
 
 	switch (conf->log->r5c_journal_mode) {
 	case R5C_JOURNAL_MODE_WRITE_THROUGH:
@@ -2557,7 +2558,9 @@ static ssize_t r5c_journal_mode_show(struct mddev *mddev, char *page)
 	default:
 		ret = 0;
 	}
-	spin_unlock(&mddev->lock);
+
+out_unlock:
+	mddev_unlock(mddev);
 	return ret;
 }
 
-- 
2.30.2