Do not call 'ima_path_check()' for each path component

Not only is that a supremely timing-critical path, but it's hopefully
some day going to be lockless for the common case, and ima can't do
that.

Plus the integrity code doesn't even care about non-regular files, so it
was always a total waste of time and effort.
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/namei.c

@@ -856,9 +856,6 @@ static int __link_path_walk(const char *name, struct nameidata *nd)
 		if (err == -EAGAIN)
 			err = inode_permission(nd->path.dentry->d_inode,
 					       MAY_EXEC);
-		if (!err)
-			err = ima_path_check(&nd->path, MAY_EXEC,
-				             IMA_COUNT_UPDATE);
  		if (err)
 			break;