linux-kernel - [PATCH 4.19 40/43] ALSA: fireface: Fix integer overflow in transmit_midi

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Date:   Mon, 18 Jan 2021 12:35:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Takashi Sakamoto <o-takashi@...amocchi.jp>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Takashi Iwai <tiwai@...e.de>
Subject: [PATCH 4.19 40/43] ALSA: fireface: Fix integer overflow in transmit_midi_msg()

From: Geert Uytterhoeven <geert+renesas@...der.be>

commit e7c22eeaff8565d9a8374f320238c251ca31480b upstream.

As snd_ff.rx_bytes[] is unsigned int, and NSEC_PER_SEC is 1000000000L,
the second multiplication in

    ff->rx_bytes[port] * 8 * NSEC_PER_SEC / 31250

always overflows on 32-bit platforms, truncating the result.  Fix this
by precalculating "NSEC_PER_SEC / 31250", which is an integer constant.

Note that this assumes ff->rx_bytes[port] <= 16777.

Fixes: 19174295788de77d ("ALSA: fireface: add transaction support")
Reviewed-by: Takashi Sakamoto <o-takashi@...amocchi.jp>
Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
Link: https://lore.kernel.org/r/20210111130251.361335-2-geert+renesas@glider.be
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 sound/firewire/fireface/ff-transaction.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/sound/firewire/fireface/ff-transaction.c
+++ b/sound/firewire/fireface/ff-transaction.c
@@ -99,7 +99,7 @@ static void transmit_midi_msg(struct snd
 
 	/* Set interval to next transaction. */
 	ff->next_ktime[port] = ktime_add_ns(ktime_get(),
-					    len * 8 * NSEC_PER_SEC / 31250);
+					    len * 8 * (NSEC_PER_SEC / 31250));
 	ff->rx_bytes[port] = len;
 
 	/*