ALSA: ctl: fix error path at adding user-defined element set

When processing request to add/replace user-defined element set, check
of given element identifier and decision of numeric identifier is done
in "__snd_ctl_add_replace()" helper function. When the result of check
is wrong, the helper function returns error code. The error code shall
be returned to userspace application.

Current implementation includes bug to return zero to userspace application
regardless of the result. This commit fixes the bug.

Cc: <stable@vger.kernel.org>
Fixes: e1a7bfe3 ("ALSA: control: Fix race between adding and removing a user element")
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20201113092043.16148-1-o-takashi@sakamocchi.jpSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/control.c

@@ -1539,7 +1539,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file,
 
  unlock:
 	up_write(&card->controls_rwsem);
-	return 0;
+	return err;
 }
 
 static int snd_ctl_elem_add_user(struct snd_ctl_file *file,