From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C5E42C433E6 for ; Thu, 18 Mar 2021 15:02:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A25A764F38 for ; Thu, 18 Mar 2021 15:02:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231658AbhCRPBt (ORCPT ); Thu, 18 Mar 2021 11:01:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33282 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231669AbhCRPB0 (ORCPT ); Thu, 18 Mar 2021 11:01:26 -0400 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2F0C1C06174A; Thu, 18 Mar 2021 08:01:26 -0700 (PDT) Received: from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi [62.78.145.57]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 22CF78E6; Thu, 18 Mar 2021 16:01:17 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1616079677; bh=ewgOcC8vQRcX5sjpoUb5TcgjDLnQNUCYxbvY2N7vYcA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TNukSGLMu8aWeM8pf/K4UQaTz4i0wM4T0Xl9N/eOzm01m5jy1FotcLFK3JyMvKdfk YOPo2hmfYZOytk8WU1UTLg0UkJWRi8ON8MxAMoUbfVfy4gwmBR2GC8F28xRab+OyIQ KmCv7tdYUaPMrHgoztS9lLCrfnGz0L/vspJ6yt3E= Date: Thu, 18 Mar 2021 17:00:39 +0200 From: Laurent Pinchart To: Arnd Bergmann Cc: Mauro Carvalho Chehab , Hans Verkuil , Arnd Bergmann , Dmitry Vyukov , syzbot+142888ffec98ab194028@syzkaller.appspotmail.com, Sakari Ailus , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] media: v4l2-core: ignore native time32 ioctls on 64-bit Message-ID: References: <20210318134334.2933141-1-arnd@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210318134334.2933141-1-arnd@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Hi Arnd, Thank you for the patch. On Thu, Mar 18, 2021 at 02:43:18PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann > > Syzbot found that passing ioctl command 0xc0505609 into a 64-bit > kernel from a 32-bit process causes uninitialized kernel memory to > get passed to drivers instead of the user space data: > > BUG: KMSAN: uninit-value in check_array_args drivers/media/v4l2-core/v4l2-ioctl.c:3041 [inline] > BUG: KMSAN: uninit-value in video_usercopy+0x1631/0x3d30 drivers/media/v4l2-core/v4l2-ioctl.c:3315 > CPU: 0 PID: 19595 Comm: syz-executor.4 Not tainted 5.11.0-rc7-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:79 [inline] > dump_stack+0x21c/0x280 lib/dump_stack.c:120 > kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118 > __msan_warning+0x5f/0xa0 mm/kmsan/kmsan_instr.c:197 > check_array_args drivers/media/v4l2-core/v4l2-ioctl.c:3041 [inline] > video_usercopy+0x1631/0x3d30 drivers/media/v4l2-core/v4l2-ioctl.c:3315 > video_ioctl2+0x9f/0xb0 drivers/media/v4l2-core/v4l2-ioctl.c:3391 > v4l2_ioctl+0x255/0x290 drivers/media/v4l2-core/v4l2-dev.c:360 > v4l2_compat_ioctl32+0x2c6/0x370 drivers/media/v4l2-core/v4l2-compat-ioctl32.c:1248 > __do_compat_sys_ioctl fs/ioctl.c:842 [inline] > __se_compat_sys_ioctl+0x53d/0x1100 fs/ioctl.c:793 > __ia32_compat_sys_ioctl+0x4a/0x70 fs/ioctl.c:793 > do_syscall_32_irqs_on arch/x86/entry/common.c:79 [inline] > __do_fast_syscall_32+0x102/0x160 arch/x86/entry/common.c:141 > do_fast_syscall_32+0x6a/0xc0 arch/x86/entry/common.c:166 > do_SYSENTER_32+0x73/0x90 arch/x86/entry/common.c:209 > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c > > The time32 commands are defined but were never meant to be called on > 64-bit machines, as those have always used time64 interfaces. I missed > this in my patch that introduced the time64 handling on 32-bit platforms. > > The problem in this case is the mismatch of one function checking for > the numeric value of the command and another function checking for the > type of process (native vs compat) instead, with the result being that > for this combination, nothing gets copied into the buffer at all. > > Avoid this by only trying to convert the time32 commands when running > on a 32-bit kernel where these are defined in a meaningful way. > > Fixes: 577c89b0ce72 ("media: v4l2-core: fix v4l2_buffer handling for time64 ABI") > Reported-by: syzbot+142888ffec98ab194028@syzkaller.appspotmail.com > Tested-by: Hans Verkuil > Signed-off-by: Arnd Bergmann v4l2_event vs. v4l2_event32 vs. v4l2_event_time32 vs. v4l2_event32_time32 is a bit confusing. Do I understand correctly that the code below runs for the non-compat path, thus native userspace (32-bit on 32-bit machines, 64-bit on 64-bit machines), and handles the case of a native userspace using a 32-bit time ? If so it indeed doesn't make sense for 64-bit machines. Reviewed-by: Laurent Pinchart > --- > This patch adds two more changes than the version that Hans tested > --- > drivers/media/v4l2-core/v4l2-ioctl.c | 6 +++--- > drivers/media/v4l2-core/v4l2-subdev.c | 2 +- > 2 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c > index 31d1342e61e8..2b1bb68dc27f 100644 > --- a/drivers/media/v4l2-core/v4l2-ioctl.c > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c > @@ -3115,7 +3115,7 @@ static int check_array_args(unsigned int cmd, void *parg, size_t *array_size, > static unsigned int video_translate_cmd(unsigned int cmd) > { > switch (cmd) { > -#ifdef CONFIG_COMPAT_32BIT_TIME > +#if !defined(CONFIG_64BIT) && defined(CONFIG_COMPAT_32BIT_TIME) > case VIDIOC_DQEVENT_TIME32: > return VIDIOC_DQEVENT; > case VIDIOC_QUERYBUF_TIME32: > @@ -3169,7 +3169,7 @@ static int video_get_user(void __user *arg, void *parg, > err = v4l2_compat_get_user(arg, parg, cmd); > } else { > switch (cmd) { > -#ifdef CONFIG_COMPAT_32BIT_TIME > +#if !defined(CONFIG_64BIT) && defined(CONFIG_COMPAT_32BIT_TIME) > case VIDIOC_QUERYBUF_TIME32: > case VIDIOC_QBUF_TIME32: > case VIDIOC_DQBUF_TIME32: > @@ -3224,7 +3224,7 @@ static int video_put_user(void __user *arg, void *parg, > return v4l2_compat_put_user(arg, parg, cmd); > > switch (cmd) { > -#ifdef CONFIG_COMPAT_32BIT_TIME > +#if !defined(CONFIG_64BIT) && defined(CONFIG_COMPAT_32BIT_TIME) > case VIDIOC_DQEVENT_TIME32: { > struct v4l2_event *ev = parg; > struct v4l2_event_time32 ev32; > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c > index 336133dbc759..9f5573d3b857 100644 > --- a/drivers/media/v4l2-core/v4l2-subdev.c > +++ b/drivers/media/v4l2-core/v4l2-subdev.c > @@ -428,7 +428,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg) > > return v4l2_event_dequeue(vfh, arg, file->f_flags & O_NONBLOCK); > > -#ifdef CONFIG_COMPAT_32BIT_TIME > +#if !defined(CONFIG_64BIT) && defined(CONFIG_COMPAT_32BIT_TIME) > case VIDIOC_DQEVENT_TIME32: { > struct v4l2_event_time32 *ev32 = arg; > struct v4l2_event ev = { }; -- Regards, Laurent Pinchart