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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 49B8DC8300C for ; Wed, 7 Jun 2023 20:20:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232550AbjFGUUt (ORCPT ); Wed, 7 Jun 2023 16:20:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232745AbjFGUUn (ORCPT ); Wed, 7 Jun 2023 16:20:43 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 331282717 for ; Wed, 7 Jun 2023 13:20:18 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 65205643AF for ; Wed, 7 Jun 2023 20:20:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7BF60C4339B; Wed, 7 Jun 2023 20:20:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1686169205; bh=7P1ovuxvTzFYSu+1MIAyr3QGwChR4p2MrkuhM2fNbD0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YoWNEZUTmuPE3PQH0PXUG+M7z6dq3C/3uNOTo0MP7g5m0dy3oMg4zgbf+nVpKe8PO RM3mNpu7W+dc04ZX1ZBTirlzDvUsoD3Fj/beQCmdcyMO/fm+3jrnJbh3SqONoobZPV FcSlKMqV3MqoceMEwcMZIOjLJvu6UOxsTrT3Y6ho= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Helge Deller , syzbot+d910bd780e6efac35869@syzkaller.appspotmail.com, Sam Ravnborg , stable@kernel.org Subject: [PATCH 4.14 54/61] fbcon: Fix null-ptr-deref in soft_cursor Date: Wed, 7 Jun 2023 22:16:08 +0200 Message-ID: <20230607200853.847389328@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230607200835.310274198@linuxfoundation.org> References: <20230607200835.310274198@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Helge Deller commit d78bd6cc68276bd57f766f7cb98bfe32c23ab327 upstream. syzbot repored this bug in the softcursor code: BUG: KASAN: null-ptr-deref in soft_cursor+0x384/0x6b4 drivers/video/fbdev/core/softcursor.c:70 Read of size 16 at addr 0000000000000200 by task kworker/u4:1/12 CPU: 0 PID: 12 Comm: kworker/u4:1 Not tainted 6.4.0-rc3-syzkaller-geb0f1697d729 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023 Workqueue: events_power_efficient fb_flashcursor Call trace: dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:233 show_stack+0x2c/0x44 arch/arm64/kernel/stacktrace.c:240 __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106 print_report+0xe4/0x514 mm/kasan/report.c:465 kasan_report+0xd4/0x130 mm/kasan/report.c:572 kasan_check_range+0x264/0x2a4 mm/kasan/generic.c:187 __asan_memcpy+0x3c/0x84 mm/kasan/shadow.c:105 soft_cursor+0x384/0x6b4 drivers/video/fbdev/core/softcursor.c:70 bit_cursor+0x113c/0x1a64 drivers/video/fbdev/core/bitblit.c:377 fb_flashcursor+0x35c/0x54c drivers/video/fbdev/core/fbcon.c:380 process_one_work+0x788/0x12d4 kernel/workqueue.c:2405 worker_thread+0x8e0/0xfe8 kernel/workqueue.c:2552 kthread+0x288/0x310 kernel/kthread.c:379 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:853 This fix let bit_cursor() bail out early when a font bitmap isn't available yet. Signed-off-by: Helge Deller Reported-by: syzbot+d910bd780e6efac35869@syzkaller.appspotmail.com Acked-by: Sam Ravnborg Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/video/fbdev/core/bitblit.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/video/fbdev/core/bitblit.c +++ b/drivers/video/fbdev/core/bitblit.c @@ -247,6 +247,9 @@ static void bit_cursor(struct vc_data *v cursor.set = 0; + if (!vc->vc_font.data) + return; + c = scr_readw((u16 *) vc->vc_pos); attribute = get_attribute(info, c); src = vc->vc_font.data + ((c & charmask) * (w * vc->vc_font.height));