From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: [PATCH] ALSA: usx2y: fix a memory leak bug Date: Mon, 29 Apr 2019 08:42:29 +0200 Message-ID: References: <1556433754-3291-1-git-send-email-wang6495@umn.edu> Mime-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Wenwen Wang Cc: "moderated list:SOUND" , Kees Cook , Jaroslav Kysela , open list List-Id: alsa-devel@alsa-project.org On Mon, 29 Apr 2019 07:50:11 +0200, Wenwen Wang wrote: > > On Mon, Apr 29, 2019 at 12:36 AM Takashi Iwai wrote: > > > > 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 > > > > > > 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. > > Thanks for your comment! Does that mean we should remove > usb_free_urb() in the if statement of allocating 'usX2Y->In04Buf', > because it may also lead to double free? Yes, that's another superfluous code. Takashi