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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Dongxiang Ke <kdx.glider@gmail.com>,
        Takashi Iwai <tiwai@suse.de>
Subject: [PATCH 4.9 31/42] ALSA: usb-audio: Fix an out-of-bounds bug in __snd_usb_parse_audio_interface()
Date:   Tue, 13 Sep 2022 16:08:02 +0200
Message-Id: <20220913140343.923046119@linuxfoundation.org>
In-Reply-To: <20220913140342.228397194@linuxfoundation.org>
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From: Dongxiang Ke <kdx.glider@gmail.com>

commit e53f47f6c1a56d2af728909f1cb894da6b43d9bf upstream.

There may be a bad USB audio device with a USB ID of (0x04fa, 0x4201) and
the number of it's interfaces less than 4, an out-of-bounds read bug occurs
when parsing the interface descriptor for this device.

Fix this by checking the number of interfaces.

Signed-off-by: Dongxiang Ke <kdx.glider@gmail.com>
Link: https://lore.kernel.org/r/20220906024928.10951-1-kdx.glider@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 sound/usb/stream.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/sound/usb/stream.c
+++ b/sound/usb/stream.c
@@ -502,7 +502,7 @@ int snd_usb_parse_audio_interface(struct
 	 * Dallas DS4201 workaround: It presents 5 altsettings, but the last
 	 * one misses syncpipe, and does not produce any sound.
 	 */
-	if (chip->usb_id == USB_ID(0x04fa, 0x4201))
+	if (chip->usb_id == USB_ID(0x04fa, 0x4201) && num >= 4)
 		num = 4;
 
 	for (i = 0; i < num; i++) {