linux-kernel - Re: [PATCH v2] ALSA: usx2y: fix a double free bug

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Date:   Mon, 29 Apr 2019 19:57:10 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     "Wenwen Wang" <wang6495@....edu>
Cc:     "moderated list:SOUND" <alsa-devel@...a-project.org>,
        "Kees Cook" <keescook@...omium.org>,
        "Jaroslav Kysela" <perex@...ex.cz>,
        "open list" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] ALSA: usx2y: fix a double free bug

On Mon, 29 Apr 2019 19:45:40 +0200,
Wenwen Wang wrote:
> 
> In usX2Y_In04_init(), a new urb is firstly created through usb_alloc_urb()
> and saved to 'usX2Y->In04urb'. Then, a buffer is allocated through
> kmalloc() and saved to 'usX2Y->In04Buf'. If the allocation of the buffer
> fails, the error code ENOMEM is returned after usb_free_urb(), which frees
> the created urb. However, the urb is actually freed at card->private_free
> callback, i.e., snd_usX2Y_card_private_free(). So the free operation here
> leads to a double free bug.
> 
> To fix the above issue, simply remove usb_free_urb().
> 
> Signed-off-by: Wenwen Wang <wang6495@....edu>

Applied now.  Thanks.


Takashi