From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752842AbcARGhb (ORCPT ); Mon, 18 Jan 2016 01:37:31 -0500 Received: from mx2.suse.de ([195.135.220.15]:42147 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751207AbcARGh3 (ORCPT ); Mon, 18 Jan 2016 01:37:29 -0500 Date: Mon, 18 Jan 2016 07:37:28 +0100 Message-ID: From: Takashi Iwai To: "Nicolas Boichat" Cc: , "Pierre-Louis Bossart" , "Jaroslav Kysela" , Subject: Re: [PATCH] ALSA: pcm: Fix snd_pcm_hw_params struct copy in compat mode In-Reply-To: <1453088958-6214-1-git-send-email-drinkcat@chromium.org> References: <1453088958-6214-1-git-send-email-drinkcat@chromium.org> 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/24.5 (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 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 18 Jan 2016 04:49:18 +0100, Nicolas Boichat wrote: > > Running a kernel with KASan enabled, we spotted that the following > read in sound/soc/soc-pcm.c:soc_pcm_hw_params() is out of bounds: > > /* copy params for each codec */ > codec_params = *params; > > The problem comes from sound/core/pcm_compat.c, > snd_pcm_ioctl_hw_params_compat, where we're copying from a > struct snd_pcm_hw_params to a struct snd_pcm_hw_params32: > > /* only fifo_size is different, so just copy all */ > data = memdup_user(data32, sizeof(*data32)); > > It turns out that snd_pcm_hw_params is 4 bytes longer than > snd_pcm_hw_params32, that's why an out-of-bounds read happens. > > We separate kmalloc and memory copy operations to make sure > data has the correct length. > > Signed-off-by: Nicolas Boichat Thanks for reporting. This is indeed effectively a revert of the commit ef44a1ec6eee ('ALSA: sound/core: use memdup_user()'), which is obviously wrong. Sigh, it's a really danger of such a "cleanup" patch. Could you rephrase the changelog mentioning the affecting commit and resubmit? Takashi > --- > sound/core/pcm_compat.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/sound/core/pcm_compat.c b/sound/core/pcm_compat.c > index b48b434..9630e9f 100644 > --- a/sound/core/pcm_compat.c > +++ b/sound/core/pcm_compat.c > @@ -255,10 +255,15 @@ static int snd_pcm_ioctl_hw_params_compat(struct snd_pcm_substream *substream, > if (! (runtime = substream->runtime)) > return -ENOTTY; > > - /* only fifo_size is different, so just copy all */ > - data = memdup_user(data32, sizeof(*data32)); > - if (IS_ERR(data)) > - return PTR_ERR(data); > + data = kmalloc(sizeof(*data), GFP_KERNEL); > + if (!data) > + return -ENOMEM; > + > + /* only fifo_size (RO from userspace) is different, so just copy all */ > + if (copy_from_user(data, data32, sizeof(*data32))) { > + err = -EFAULT; > + goto error; > + } > > if (refine) > err = snd_pcm_hw_refine(substream, data); > -- > 2.6.0.rc2.230.g3dd15c0 > >