[PATCH] procfs: Fix a locking bug in a vmcore_add_device_dump() error path

[Bart Van Assche <bvanassche@xxxxxxx>]

Unlock vmcore_mutex when returning -EBUSY.

Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Fixes: 0f3b1c40c652 ("fs/proc/vmcore: disallow vmcore modifications while the vmcore is open")
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
 fs/proc/vmcore.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index a00120a3c099..10d01eb09c43 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -1524,7 +1524,7 @@ int vmcore_add_device_dump(struct vmcoredd_data *data)
 		pr_warn_once("Unexpected adding of device dump\n");
 	if (vmcore_open) {
 		ret = -EBUSY;
-		goto out_err;
+		goto unlock;
 	}
 
 	list_add_tail(&dump->list, &vmcoredd_list);
@@ -1532,6 +1532,9 @@ int vmcore_add_device_dump(struct vmcoredd_data *data)
 	mutex_unlock(&vmcore_mutex);
 	return 0;
 
+unlock:
+	mutex_unlock(&vmcore_mutex);
+
 out_err:
 	vfree(buf);
 	vfree(dump);