smb3: fix lock ordering potential deadlock in cifs_sync_mid_result

Coverity spotted that the cifs_sync_mid_result function could deadlock

"Thread deadlock (ORDER_REVERSAL) lock_order: Calling spin_lock acquires
lock TCP_Server_Info.srv_lock while holding lock TCP_Server_Info.mid_lock"

Addresses-Coverity: 1590401 ("Thread deadlock (ORDER_REVERSAL)")
Cc: stable@vger.kernel.org
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/client/transport.c b/fs/smb/client/transport.c
index e1a79e031b28ccc85571720bc0510c219bc8daef..ddf1a3aafee5c6f1e4f9c6ed4db54c48fcc8a84a 100644 (file)
--- a/fs/smb/client/transport.c
+++ b/fs/smb/client/transport.c
@@ -909,12 +909,15 @@ cifs_sync_mid_result(struct mid_q_entry *mid, struct TCP_Server_Info *server)
                        list_del_init(&mid->qhead);
                        mid->mid_flags |= MID_DELETED;
                }
+               spin_unlock(&server->mid_lock);
                cifs_server_dbg(VFS, "%s: invalid mid state mid=%llu state=%d\n",
                         __func__, mid->mid, mid->mid_state);
                rc = -EIO;
+               goto sync_mid_done;
        }
        spin_unlock(&server->mid_lock);
 
+sync_mid_done:
        release_mid(mid);
        return rc;
 }