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=-10.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 5547BC433E0 for ; Tue, 28 Jul 2020 12:35:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3AB492070B for ; Tue, 28 Jul 2020 12:35:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729795AbgG1MfW convert rfc822-to-8bit (ORCPT ); Tue, 28 Jul 2020 08:35:22 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:57397 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729282AbgG1MfV (ORCPT ); Tue, 28 Jul 2020 08:35:21 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-138-aKECZJEyMU60G_8cxFq3Wg-1; Tue, 28 Jul 2020 13:35:18 +0100 X-MC-Unique: aKECZJEyMU60G_8cxFq3Wg-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Tue, 28 Jul 2020 13:35:17 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Tue, 28 Jul 2020 13:35:17 +0100 From: David Laight To: 'Peilin Ye' , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann CC: David Airlie , Daniel Vetter , "Dan Carpenter" , Arnd Bergmann , "Greg Kroah-Hartman" , "linux-kernel-mentees@lists.linuxfoundation.org" , "dri-devel@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" Subject: RE: [Linux-kernel-mentees] [PATCH v2] drm/bufs: Prevent kernel-infoleak in copy_one_buf() Thread-Topic: [Linux-kernel-mentees] [PATCH v2] drm/bufs: Prevent kernel-infoleak in copy_one_buf() Thread-Index: AQHWZNW9oERUOmwTgUadWvPHDViznqkc48JA Date: Tue, 28 Jul 2020 12:35:17 +0000 Message-ID: <3058d741282b463d8aa7c8aff62e4326@AcuMS.aculab.com> References: <20200728014343.341303-1-yepeilin.cs@gmail.com> <20200728115210.408486-1-yepeilin.cs@gmail.com> In-Reply-To: <20200728115210.408486-1-yepeilin.cs@gmail.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peilin Ye > Sent: 28 July 2020 12:52 > Currently `struct drm_buf_desc` is defined as follows: > > struct drm_buf_desc { > int count; > int size; > int low_mark; > int high_mark; > enum { > _DRM_PAGE_ALIGN = 0x01, > _DRM_AGP_BUFFER = 0x02, > _DRM_SG_BUFFER = 0x04, > _DRM_FB_BUFFER = 0x08, > _DRM_PCI_BUFFER_RO = 0x10 > } flags; > unsigned long agp_start; > }; > > copy_one_buf() is potentially copying uninitialized kernel stack memory > to userspace, since the compiler may leave such "holes" (around `.flags` > and `.agp_start` fields) in this statically allocated structure. Prevent > it by initializing `v` with memset(). > > Cc: stable@vger.kernel.org > Fixes: 5c7640ab6258 ("switch compat_drm_infobufs() to drm_ioctl_kernel()") > Suggested-by: Dan Carpenter > Acked-by: Arnd Bergmann > Signed-off-by: Peilin Ye > --- > Change in v2: > - Improve commit description. (Suggested by Arnd Bergmann > ) > > drivers/gpu/drm/drm_bufs.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/drm_bufs.c b/drivers/gpu/drm/drm_bufs.c > index a0735fbc144b..f99cd4a3f951 100644 > --- a/drivers/gpu/drm/drm_bufs.c > +++ b/drivers/gpu/drm/drm_bufs.c > @@ -1349,10 +1349,14 @@ static int copy_one_buf(void *data, int count, struct drm_buf_entry *from) > { > struct drm_buf_info *request = data; > struct drm_buf_desc __user *to = &request->list[count]; > - struct drm_buf_desc v = {.count = from->buf_count, > - .size = from->buf_size, > - .low_mark = from->low_mark, > - .high_mark = from->high_mark}; > + struct drm_buf_desc v; > + > + memset(&v, 0, sizeof(v)); > + > + v.count = from->buf_count; > + v.size = from->buf_size; > + v.low_mark = from->low_mark; > + v.high_mark = from->high_mark; > > if (copy_to_user(to, &v, offsetof(struct drm_buf_desc, flags))) > return -EFAULT; The memset() isn't needed. The copy_to_user() stops after the 4 'int' values so no 'random' kernel stack can get copied. Quite why it is 'right' to leave the remaining part of each userspace structure unchanged is another matter. David. - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)