jffs2_kill_sb(): deal with failed allocations

BugLink: http://bugs.launchpad.net/bugs/1768429

commit c66b23c2 upstream.

jffs2_fill_super() might fail to allocate jffs2_sb_info;
jffs2_kill_sb() must survive that.

Cc: stable@kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

fs/jffs2/super.c

@@ -345,7 +345,7 @@ static void jffs2_put_super (struct super_block *sb)
 static void jffs2_kill_sb(struct super_block *sb)
 {
 	struct jffs2_sb_info *c = JFFS2_SB_INFO(sb);
-	if (!(sb->s_flags & MS_RDONLY))
+	if (c && !(sb->s_flags & MS_RDONLY))
 		jffs2_stop_garbage_collect_thread(c);
 	kill_mtd_super(sb);
 	kfree(c);