Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 12 Jan 2021 14:58:47 +0100
Message-ID: <s5hsg76qmso.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Geert Uytterhoeven <geert+renesas@glider.be>
Cc:     Clemens Ladisch <clemens@ladisch.de>,
        Takashi Sakamoto <o-takashi@sakamocchi.jp>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>, alsa-devel@alsa-project.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH/RFC 2/2] ALSA: firewire-tascam: Fix integer overflow in midi_port_work()
In-Reply-To: <20210111130251.361335-3-geert+renesas@glider.be>
References: <20210111130251.361335-1-geert+renesas@glider.be>
        <20210111130251.361335-3-geert+renesas@glider.be>
User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka)
 FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3
 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO)
MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka")
Content-Type: text/plain; charset=US-ASCII
Precedence: bulk

On Mon, 11 Jan 2021 14:02:51 +0100,
Geert Uytterhoeven wrote:
> 
> As snd_fw_async_midi_port.consume_bytes is unsigned int, and
> NSEC_PER_SEC is 1000000000L, the second multiplication in
> 
>     port->consume_bytes * 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 port->consume_bytes <= 16777.
> 
> Fixes: 531f471834227d03 ("ALSA: firewire-lib/firewire-tascam: localize async midi port")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> Compile-tested only.
> 
> I don't know the maximum transfer length of MIDI, but given it's an old
> standard, I guess it's rather small.  If it is larger than 16777, the
> constant "8" should be replaced by "8ULL", to force 64-bit arithmetic.

Applied now.  Thanks.


Takashi