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 1A960C07E99 for ; Mon, 12 Jul 2021 14:37:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EF56A61156 for ; Mon, 12 Jul 2021 14:37:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235209AbhGLOkl (ORCPT ); Mon, 12 Jul 2021 10:40:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58536 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235179AbhGLOkk (ORCPT ); Mon, 12 Jul 2021 10:40:40 -0400 Received: from mail-wm1-x335.google.com (mail-wm1-x335.google.com [IPv6:2a00:1450:4864:20::335]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1ADB8C0613E5 for ; Mon, 12 Jul 2021 07:37:52 -0700 (PDT) Received: by mail-wm1-x335.google.com with SMTP id b14-20020a1c1b0e0000b02901fc3a62af78so14593601wmb.3 for ; Mon, 12 Jul 2021 07:37:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=date:from:to:cc:subject:message-id:mail-followup-to:references :mime-version:content-disposition:in-reply-to; bh=5MvsjY4pTEd5k29K3lYAodvANPB7dCwy0fDdN4Dc+OU=; b=DL95kZw7btL3htFTaW94KekmngiAohubrwxs52d8zHcU2Pbn5FIq7Y1SsbA7R09BqS eFcpL7PqpCyuTqLIAzpNm23Z04Gqg/XOiVnaxa2X0FlakC/xkAJkHizc8EUURhyOzF/s RLdM1aY0/8HeyoOOqmiWLFcb9UmOz8UikBLp4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id :mail-followup-to:references:mime-version:content-disposition :in-reply-to; bh=5MvsjY4pTEd5k29K3lYAodvANPB7dCwy0fDdN4Dc+OU=; b=sGHWYiVJ2nK0Gv3rCboa+3EGXbE4nSTOwcgQcCBRFZtHYj8NHz5JNQNjk+QhLccuzX cIUsZ+c0ZN8e+pg9i7QUEe/B/nJocyGxusP6mS5HQBv/HGFTV8jpKMH2J6A6xYwe3wnB zJSzUr/3n4npQGQPxY+P7WzyB06Rrvq2lMH/icKHvXRBzuGxLd2BpUQWsne7H8fQAHtB Nt1u6bZZ3yBhsBRvARdcGxFV/BBpqi7AJN5F0Hafywb/6/Fkvdz+kVE0iQ0si2mlaJ/j N9IcUR+NE5rUfB/Nflx/UEXbLKfgRKpeGDxW/zbo+BVH1vMOh2IIY/lwHyTxOJkh/JPD 5W4g== X-Gm-Message-State: AOAM532vBojham+fHB7yJDhfDokY0WA4rss81ulWuke+tRtD97BWLs6I 5dWRAHPpXkIlY1QOScPIfzJHDw== X-Google-Smtp-Source: ABdhPJxQay/+e0GLtdI0ff33EQHMLSIiRe5WWhtjGOPQLPgpU8vOTCjIMVM1pdQ7c3u9d0Pa7Ymgqw== X-Received: by 2002:a05:600c:1d1f:: with SMTP id l31mr3197939wms.26.1626100670687; Mon, 12 Jul 2021 07:37:50 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id l20sm13057801wmq.3.2021.07.12.07.37.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Jul 2021 07:37:49 -0700 (PDT) Date: Mon, 12 Jul 2021 16:37:48 +0200 From: Daniel Vetter To: Zhen Lei Cc: Daniel Vetter , Sam Ravnborg , dri-devel , linux-fbdev , linux-kernel , Maarten Lankhorst Subject: Re: [PATCH 1/1] fbmem: Do not delete the mode that is still in use Message-ID: Mail-Followup-To: Zhen Lei , Sam Ravnborg , dri-devel , linux-fbdev , linux-kernel , Maarten Lankhorst References: <20210712085544.2828-1-thunder.leizhen@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210712085544.2828-1-thunder.leizhen@huawei.com> X-Operating-System: Linux phenom 5.10.0-7-amd64 Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org On Mon, Jul 12, 2021 at 04:55:44PM +0800, Zhen Lei wrote: > The execution of fb_delete_videomode() is not based on the result of the > previous fbcon_mode_deleted(). As a result, the mode is directly deleted, > regardless of whether it is still in use, which may cause UAF. > > ================================================================== > BUG: KASAN: use-after-free in fb_mode_is_equal+0x36e/0x5e0 \ > drivers/video/fbdev/core/modedb.c:924 > Read of size 4 at addr ffff88807e0ddb1c by task syz-executor.0/18962 > > CPU: 2 PID: 18962 Comm: syz-executor.0 Not tainted 5.10.45-rc1+ #3 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ... > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x137/0x1be lib/dump_stack.c:118 > print_address_description+0x6c/0x640 mm/kasan/report.c:385 > __kasan_report mm/kasan/report.c:545 [inline] > kasan_report+0x13d/0x1e0 mm/kasan/report.c:562 > fb_mode_is_equal+0x36e/0x5e0 drivers/video/fbdev/core/modedb.c:924 > fbcon_mode_deleted+0x16a/0x220 drivers/video/fbdev/core/fbcon.c:2746 > fb_set_var+0x1e1/0xdb0 drivers/video/fbdev/core/fbmem.c:975 > do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108 > vfs_ioctl fs/ioctl.c:48 [inline] > __do_sys_ioctl fs/ioctl.c:753 [inline] > __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739 > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Freed by task 18960: > kasan_save_stack mm/kasan/common.c:48 [inline] > kasan_set_track+0x3d/0x70 mm/kasan/common.c:56 > kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355 > __kasan_slab_free+0x108/0x140 mm/kasan/common.c:422 > slab_free_hook mm/slub.c:1541 [inline] > slab_free_freelist_hook+0xd6/0x1a0 mm/slub.c:1574 > slab_free mm/slub.c:3139 [inline] > kfree+0xca/0x3d0 mm/slub.c:4121 > fb_delete_videomode+0x56a/0x820 drivers/video/fbdev/core/modedb.c:1104 > fb_set_var+0x1f3/0xdb0 drivers/video/fbdev/core/fbmem.c:978 > do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108 > vfs_ioctl fs/ioctl.c:48 [inline] > __do_sys_ioctl fs/ioctl.c:753 [inline] > __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739 > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Fixes: 13ff178ccd6d ("fbcon: Call fbcon_mode_deleted/new_modelist directly") > Signed-off-by: Zhen Lei Nice catch, that indeed got lost. Reviewed-by: Daniel Vetter Cc: # v5.3+ Needs to be applied to drm-misc-fixes, but the tree isn't ready yet. -Daniel > --- > drivers/video/fbdev/core/fbmem.c | 12 +++++------- > 1 file changed, 5 insertions(+), 7 deletions(-) > > diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c > index 98f193078c05..1c855145711b 100644 > --- a/drivers/video/fbdev/core/fbmem.c > +++ b/drivers/video/fbdev/core/fbmem.c > @@ -970,13 +970,11 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var) > fb_var_to_videomode(&mode2, &info->var); > /* make sure we don't delete the videomode of current var */ > ret = fb_mode_is_equal(&mode1, &mode2); > - > - if (!ret) > - fbcon_mode_deleted(info, &mode1); > - > - if (!ret) > - fb_delete_videomode(&mode1, &info->modelist); > - > + if (!ret) { > + ret = fbcon_mode_deleted(info, &mode1); > + if (!ret) > + fb_delete_videomode(&mode1, &info->modelist); > + } > > return ret ? -EINVAL : 0; > } > -- > 2.25.1 > > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch