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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,
        syzbot+df7dc146ebdd6435eea3@syzkaller.appspotmail.com,
        Takashi Iwai <tiwai@suse.de>
Subject: [PATCH 5.9 37/49] ALSA: usb-audio: Fix potential out-of-bounds shift
Date:   Sat, 19 Dec 2020 13:58:41 +0100
Message-Id: <20201219125346.486923224@linuxfoundation.org>
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From: Takashi Iwai <tiwai@suse.de>

commit 43d5ca88dfcd35e43010fdd818e067aa9a55f5ba upstream.

syzbot spotted a potential out-of-bounds shift in the USB-audio format
parser that receives the arbitrary shift value from the USB
descriptor.

Add a range check for avoiding the undefined behavior.

Reported-by: syzbot+df7dc146ebdd6435eea3@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201209084552.17109-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/usb/format.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/sound/usb/format.c
+++ b/sound/usb/format.c
@@ -40,6 +40,8 @@ static u64 parse_audio_format_i_type(str
 	case UAC_VERSION_1:
 	default: {
 		struct uac_format_type_i_discrete_descriptor *fmt = _fmt;
+		if (format >= 64)
+			return 0; /* invalid format */
 		sample_width = fmt->bBitResolution;
 		sample_bytes = fmt->bSubframeSize;
 		format = 1ULL << format;