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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 99CA7C2D0EB for ; Mon, 30 Mar 2020 19:16:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 801E620771 for ; Mon, 30 Mar 2020 19:16:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728255AbgC3TQ2 (ORCPT ); Mon, 30 Mar 2020 15:16:28 -0400 Received: from asavdk3.altibox.net ([109.247.116.14]:47348 "EHLO asavdk3.altibox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726672AbgC3TQ2 (ORCPT ); Mon, 30 Mar 2020 15:16:28 -0400 Received: from ravnborg.org (unknown [158.248.194.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by asavdk3.altibox.net (Postfix) with ESMTPS id 7155D20024; Mon, 30 Mar 2020 21:16:20 +0200 (CEST) Date: Mon, 30 Mar 2020 21:16:19 +0200 From: Sam Ravnborg To: Qiujun Huang , Bartlomiej Zolnierkiewicz Cc: b.zolnierkie@samsung.com, daniel.vetter@ffwll.ch, maarten.lankhorst@linux.intel.com, daniel.thompson@linaro.org, ghalat@redhat.com, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] fbcon: fix null-ptr-deref in fbcon_switch Message-ID: <20200330191619.GF7594@ravnborg.org> References: <20200329085647.25133-1-hqjagain@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200329085647.25133-1-hqjagain@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CMAE-Score: 0 X-CMAE-Analysis: v=2.3 cv=eMA9ckh1 c=1 sm=1 tr=0 a=UWs3HLbX/2nnQ3s7vZ42gw==:117 a=UWs3HLbX/2nnQ3s7vZ42gw==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=D19gQVrFAAAA:8 a=hSkVLCK3AAAA:8 a=pGLkceISAAAA:8 a=7gkXJVJtAAAA:8 a=NVFoAeSCgwShZuBWzHEA:9 a=ViYWLu_RVrLAkblt:21 a=QLy0bD8Az-XStLsx:21 a=CjuIK1q_8ugA:10 a=W4TVW4IDbPiebHqcZpNg:22 a=cQPPKAXgyycSBL8etih5:22 a=E9Po1WZjFZOl8hwRPBS3:22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Qiujun On Sun, Mar 29, 2020 at 04:56:47PM +0800, Qiujun Huang wrote: > Set logo_shown to FBCON_LOGO_CANSHOW when the vc was deallocated. > > syzkaller report: https://lkml.org/lkml/2020/3/27/403 > general protection fault, probably for non-canonical address > 0xdffffc000000006c: 0000 [#1] SMP KASAN > KASAN: null-ptr-deref in range [0x0000000000000360-0x0000000000000367] > RIP: 0010:fbcon_switch+0x28f/0x1740 > drivers/video/fbdev/core/fbcon.c:2260 > > Call Trace: > redraw_screen+0x2a8/0x770 drivers/tty/vt/vt.c:1008 > vc_do_resize+0xfe7/0x1360 drivers/tty/vt/vt.c:1295 > fbcon_init+0x1221/0x1ab0 drivers/video/fbdev/core/fbcon.c:1219 > visual_init+0x305/0x5c0 drivers/tty/vt/vt.c:1062 > do_bind_con_driver+0x536/0x890 drivers/tty/vt/vt.c:3542 > do_take_over_console+0x453/0x5b0 drivers/tty/vt/vt.c:4122 > do_fbcon_takeover+0x10b/0x210 drivers/video/fbdev/core/fbcon.c:588 > fbcon_fb_registered+0x26b/0x340 drivers/video/fbdev/core/fbcon.c:3259 > do_register_framebuffer drivers/video/fbdev/core/fbmem.c:1664 [inline] > register_framebuffer+0x56e/0x980 drivers/video/fbdev/core/fbmem.c:1832 > dlfb_usb_probe.cold+0x1743/0x1ba3 drivers/video/fbdev/udlfb.c:1735 > usb_probe_interface+0x310/0x800 drivers/usb/core/driver.c:374 > > accessing vc_cons[logo_shown].d->vc_top causes the bug. > > Reported-by: syzbot+732528bae351682f1f27@syzkaller.appspotmail.com > Signed-off-by: Qiujun Huang > --- > drivers/video/fbdev/core/fbcon.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c > index bb6ae995c2e5..5eb3fc90f9f6 100644 > --- a/drivers/video/fbdev/core/fbcon.c > +++ b/drivers/video/fbdev/core/fbcon.c > @@ -1283,6 +1283,9 @@ static void fbcon_deinit(struct vc_data *vc) > if (!con_is_bound(&fb_con)) > fbcon_exit(); > > + if (vc->vc_num == logo_shown) > + logo_shown = FBCON_LOGO_CANSHOW; > + > return; > } Looks much better than the previous version. Acked-by: Sam Ravnborg I expect Bartlomiej to review/apply. Sam