9p: do not crash on unknown lock status code

Current 9p implementation will crash whole system if sees unknown lock
status code. It's trivial target for DOS: 9p server can produce such
code easily.

Let's fallback more gracefully: warning in dmesg + -ENOLCK.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 8d29e1e03dfa..9612e5fc0ae2 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -212,12 +212,13 @@ static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
         case P9_LOCK_BLOCKED:
                 res = -EAGAIN;
                 break;
+        default:
+                WARN_ONCE(1, "unknown lock status code: %d\n", status);
+                /* fallthough */
         case P9_LOCK_ERROR:
         case P9_LOCK_GRACE:
                 res = -ENOLCK;
                 break;
-        default:
-                BUG();
         }
 
 out_unlock: