linux-kernel - Re: [PATCH] ALSA: usx2y: fix a memory leak bug

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Message-ID: <s5ha7g9l6ea.wl-tiwai@suse.de>
Date:   Mon, 29 Apr 2019 07:36:29 +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] ALSA: usx2y: fix a memory leak bug

On Sun, 28 Apr 2019 09:18:40 +0200,
Takashi Iwai wrote:
> 
> On Sun, 28 Apr 2019 08:42:32 +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'. After the urb is initialized, a
> > sanity check is performed for the endpoint in the urb by invoking
> > usb_urb_ep_type_check(). If the check fails, the error code EINVAL will be
> > returned. In that case, however, the created urb and the allocated buffer
> > are not freed, leading to memory leaks.
> > 
> > To fix the above issue, free the urb and the buffer if the check fails.
> > 
> > Signed-off-by: Wenwen Wang <wang6495@....edu>
> 
> Applied now, thanks.

... and looking at the code again, this patch turned out to be wrong.
The in04 urb and transfer buffer are freed at card->private_free
callback (snd_usX2Y_card_private_free()) later, so this patch would
lead to double-free.

I dropped the patch now.


thanks,

Takashi