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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 4C9B9C433DB for ; Sat, 23 Jan 2021 10:07:31 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C69FF22273 for ; Sat, 23 Jan 2021 10:07:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C69FF22273 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58470 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l3FpJ-0001XQ-GC for qemu-devel@archiver.kernel.org; Sat, 23 Jan 2021 05:07:29 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:45710) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l3Fo1-0000sn-Ee for qemu-devel@nongnu.org; Sat, 23 Jan 2021 05:06:09 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:47829) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l3Fnw-0003Ul-DP for qemu-devel@nongnu.org; Sat, 23 Jan 2021 05:06:07 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611396361; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=iDV+fAnpYxRRMENpO3wSS90PgF487Vfo9BsKde0DiGw=; b=hRHFg68h9/4GviE/fi5jk/8yplU3VfU+O50pirzfPs9kYMKeupVI8Y1kT4BYz6//S0312p O0qiu4q1VCl82ogkkNGThfG/IfM3k3NWDre+jIJwICsq+0Jj/zkkjKKAR8KZ+8gyWoJULC 7I3Nntvbojrqesd9MuBbBBFizNhS5nY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-521-10QSqrsrMbiq7wVO9y_Aaw-1; Sat, 23 Jan 2021 05:05:58 -0500 X-MC-Unique: 10QSqrsrMbiq7wVO9y_Aaw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E3943801817; Sat, 23 Jan 2021 10:05:56 +0000 (UTC) Received: from localhost.localdomain (ovpn-112-11.phx2.redhat.com [10.3.112.11]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CC34F71C9D; Sat, 23 Jan 2021 10:05:54 +0000 (UTC) From: P J P To: John Snow Subject: [PATCH] fdc: check drive block device before usage (CVE-2021-20196) Date: Sat, 23 Jan 2021 15:33:45 +0530 Message-Id: <20210123100345.642933-1-ppandit@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=ppandit@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="US-ASCII" Received-SPF: pass client-ip=216.205.24.124; envelope-from=ppandit@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.182, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Gaoning Pan , QEMU Developers , Prasad J Pandit Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Prasad J Pandit While processing ioport command in 'fdctrl_write_dor', device controller may select a drive which is not initialised with a block device. This may result in a NULL pointer dereference. Add checks to avoid it. Fixes: CVE-2021-20196 Reported-by: Gaoning Pan Buglink: https://bugs.launchpad.net/qemu/+bug/1912780 Signed-off-by: Prasad J Pandit --- hw/block/fdc.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/hw/block/fdc.c b/hw/block/fdc.c index 3636874432..13a9470d19 100644 --- a/hw/block/fdc.c +++ b/hw/block/fdc.c @@ -1429,7 +1429,9 @@ static void fdctrl_write_dor(FDCtrl *fdctrl, uint32_t value) } } /* Selected drive */ - fdctrl->cur_drv = value & FD_DOR_SELMASK; + if (fdctrl->drives[value & FD_DOR_SELMASK].blk) { + fdctrl->cur_drv = value & FD_DOR_SELMASK; + } fdctrl->dor = value; } @@ -1894,6 +1896,10 @@ static uint32_t fdctrl_read_data(FDCtrl *fdctrl) uint32_t pos; cur_drv = get_cur_drv(fdctrl); + if (!cur_drv->blk) { + FLOPPY_DPRINTF("No drive connected\n"); + return 0; + } fdctrl->dsr &= ~FD_DSR_PWRDOWN; if (!(fdctrl->msr & FD_MSR_RQM) || !(fdctrl->msr & FD_MSR_DIO)) { FLOPPY_DPRINTF("error: controller not ready for reading\n"); @@ -2420,7 +2426,8 @@ static void fdctrl_write_data(FDCtrl *fdctrl, uint32_t value) if (pos == FD_SECTOR_LEN - 1 || fdctrl->data_pos == fdctrl->data_len) { cur_drv = get_cur_drv(fdctrl); - if (blk_pwrite(cur_drv->blk, fd_offset(cur_drv), fdctrl->fifo, + if (cur_drv->blk == NULL + || blk_pwrite(cur_drv->blk, fd_offset(cur_drv), fdctrl->fifo, BDRV_SECTOR_SIZE, 0) < 0) { FLOPPY_DPRINTF("error writing sector %d\n", fd_sector(cur_drv)); -- 2.29.2