From mboxrd@z Thu Jan  1 00:00:00 1970
From: Takashi Iwai <tiwai@suse.de>
Subject: Re: [PATCH] ALSA: usb-audio: Fix out-of-bound error
Date: Wed, 15 Nov 2017 10:16:18 +0100
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To: Jaejoong Kim <climbbb.kim@gmail.com>
Cc: Jaroslav Kysela <perex@perex.cz>, stable@vger.kernel.org, alsa-devel@alsa-project.org
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On Wed, 15 Nov 2017 09:57:56 +0100,
Jaejoong Kim wrote:
> 
> diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
> index e630813..5a83c2c 100644
> --- a/sound/usb/mixer.c
> +++ b/sound/usb/mixer.c
> @@ -204,7 +204,8 @@ static int snd_usb_copy_string_desc(struct mixer_build
> *state,
>                                     int index, char *buf, int maxlen)
>  {
>         int len = usb_string(state->chip->dev, index, buf, maxlen - 1);
> -       buf[len] = 0;
> +       if (len > 0)
> +               buf[len] = 0;
>         return len;

I'd rather put an explicit error bail-out, i.e.

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 91bc8f18791e..296a63a9d09c 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -204,6 +204,10 @@ static int snd_usb_copy_string_desc(struct mixer_build *state,
 				    int index, char *buf, int maxlen)
 {
 	int len = usb_string(state->chip->dev, index, buf, maxlen - 1);
+
+	if (len < 0)
+		return len;
+
 	buf[len] = 0;
 	return len;
 }


thanks,

Takashi