linux-kernel - Re: [PATCH] ALSA: usb-audio: Fix usb audio refcnt leak when getting spdif

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Date:   Thu, 23 Apr 2020 09:11:10 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Xiyu Yang <xiyuyang19@...an.edu.cn>
Cc:     Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        Xin Tan <tanxin.ctf@...il.com>,
        "Geoffrey D. Bennett" <g@...vu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Colin Ian King <colin.king@...onical.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        yuanxzhang@...an.edu.cn, kjlu@....edu
Subject: Re: [PATCH] ALSA: usb-audio: Fix usb audio refcnt leak when getting spdif

On Thu, 23 Apr 2020 06:54:19 +0200,
Xiyu Yang wrote:
> 
> snd_microii_spdif_default_get() invokes snd_usb_lock_shutdown(), which
> increases the refcount of the snd_usb_audio object "chip".
> 
> When snd_microii_spdif_default_get() returns, local variable "chip"
> becomes invalid, so the refcount should be decreased to keep refcount
> balanced.
> 
> The reference counting issue happens in several exception handling paths
> of snd_microii_spdif_default_get(). When those error scenarios occur
> such as usb_ifnum_to_if() returns NULL, the function forgets to decrease
> the refcnt increased by snd_usb_lock_shutdown(), causing a refcnt leak.
> 
> Fix this issue by jumping to "end" label when those error scenarios
> occur.
> 
> Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@...il.com>

Applied now (with Cc-to-stable and Fixes tags).


thanks,

Takashi