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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jan Kara <jack@suse.cz>,
        Jens Axboe <axboe@kernel.dk>
Subject: [PATCH 4.20 100/111] loop: Push loop_ctl_mutex down to loop_get_status()
Date:   Mon, 21 Jan 2019 14:43:34 +0100
Message-Id: <20190121122506.652884846@linuxfoundation.org>
In-Reply-To: <20190121122455.819406896@linuxfoundation.org>
References: <20190121122455.819406896@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jan Kara <jack@suse.cz>

commit 4a5ce9ba5877e4640200d84a735361306ad1a1b8 upstream.

Push loop_ctl_mutex down to loop_get_status() to avoid the unusual
convention that the function gets called with loop_ctl_mutex held and
releases it.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/block/loop.c |   37 ++++++++++---------------------------
 1 file changed, 10 insertions(+), 27 deletions(-)

--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1232,6 +1232,9 @@ loop_get_status(struct loop_device *lo,
 	struct kstat stat;
 	int ret;
 
+	ret = mutex_lock_killable_nested(&loop_ctl_mutex, 1);
+	if (ret)
+		return ret;
 	if (lo->lo_state != Lo_bound) {
 		mutex_unlock(&loop_ctl_mutex);
 		return -ENXIO;
@@ -1346,10 +1349,8 @@ loop_get_status_old(struct loop_device *
 	struct loop_info64 info64;
 	int err;
 
-	if (!arg) {
-		mutex_unlock(&loop_ctl_mutex);
+	if (!arg)
 		return -EINVAL;
-	}
 	err = loop_get_status(lo, &info64);
 	if (!err)
 		err = loop_info64_to_old(&info64, &info);
@@ -1364,10 +1365,8 @@ loop_get_status64(struct loop_device *lo
 	struct loop_info64 info64;
 	int err;
 
-	if (!arg) {
-		mutex_unlock(&loop_ctl_mutex);
+	if (!arg)
 		return -EINVAL;
-	}
 	err = loop_get_status(lo, &info64);
 	if (!err && copy_to_user(arg, &info64, sizeof(info64)))
 		err = -EFAULT;
@@ -1477,12 +1476,7 @@ static int lo_ioctl(struct block_device
 		}
 		break;
 	case LOOP_GET_STATUS:
-		err = mutex_lock_killable_nested(&loop_ctl_mutex, 1);
-		if (err)
-			return err;
-		err = loop_get_status_old(lo, (struct loop_info __user *) arg);
-		/* loop_get_status() unlocks loop_ctl_mutex */
-		break;
+		return loop_get_status_old(lo, (struct loop_info __user *) arg);
 	case LOOP_SET_STATUS64:
 		err = -EPERM;
 		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN)) {
@@ -1495,12 +1489,7 @@ static int lo_ioctl(struct block_device
 		}
 		break;
 	case LOOP_GET_STATUS64:
-		err = mutex_lock_killable_nested(&loop_ctl_mutex, 1);
-		if (err)
-			return err;
-		err = loop_get_status64(lo, (struct loop_info64 __user *) arg);
-		/* loop_get_status() unlocks loop_ctl_mutex */
-		break;
+		return loop_get_status64(lo, (struct loop_info64 __user *) arg);
 	case LOOP_SET_CAPACITY:
 	case LOOP_SET_DIRECT_IO:
 	case LOOP_SET_BLOCK_SIZE:
@@ -1625,10 +1614,8 @@ loop_get_status_compat(struct loop_devic
 	struct loop_info64 info64;
 	int err;
 
-	if (!arg) {
-		mutex_unlock(&loop_ctl_mutex);
+	if (!arg)
 		return -EINVAL;
-	}
 	err = loop_get_status(lo, &info64);
 	if (!err)
 		err = loop_info64_to_compat(&info64, arg);
@@ -1651,12 +1638,8 @@ static int lo_compat_ioctl(struct block_
 		}
 		break;
 	case LOOP_GET_STATUS:
-		err = mutex_lock_killable(&loop_ctl_mutex);
-		if (!err) {
-			err = loop_get_status_compat(lo,
-						     (struct compat_loop_info __user *)arg);
-			/* loop_get_status() unlocks loop_ctl_mutex */
-		}
+		err = loop_get_status_compat(lo,
+				     (struct compat_loop_info __user *)arg);
 		break;
 	case LOOP_SET_CAPACITY:
 	case LOOP_CLR_FD: