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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 0E8B2C76191 for ; Fri, 26 Jul 2019 13:56:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D89FF22CE5 for ; Fri, 26 Jul 2019 13:56:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564149401; bh=v4I0YP9S8oq/DoVG4zaJ1ONi/u5H9SWHkZSHNkrTCsM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=K24izFaOevW1F2GfWbgls4mv3K1mAagio+2tHVTwYvKp3mrZ4BBdS9btoDe2VLCZf uhQhir3ZWiKlSQiBRsUOCh7eJ0XLHp4aEeBps0oNQOm6LRr6XSBlzywz2csHYsUQGW Stt/WP8fpPH1Rblxy7VxuKdWp58OEN+oXpdR+9WQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387767AbfGZNlr (ORCPT ); Fri, 26 Jul 2019 09:41:47 -0400 Received: from mail.kernel.org ([198.145.29.99]:48264 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387732AbfGZNlm (ORCPT ); Fri, 26 Jul 2019 09:41:42 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 12CF422CC0; Fri, 26 Jul 2019 13:41:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564148501; bh=v4I0YP9S8oq/DoVG4zaJ1ONi/u5H9SWHkZSHNkrTCsM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=L3xgxuLXFSoENX6FQrBUTNz2Oh/kXrTmrFJ45xUNKOnXpXe5OMiRoStuOExhjdciM WYU70JSrFe3apCgqc/oWELGU2t5QtXJPLeWUT3NNEFjhAxwXg7GhD0OBcHpXlybCDK cbRafXTCnPt3fxNZAh69bj7PmYVpDXpiH39ajJus= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Denis Efremov , Willy Tarreau , Linus Torvalds , Sasha Levin , linux-block@vger.kernel.org Subject: [PATCH AUTOSEL 5.2 69/85] floppy: fix div-by-zero in setup_format_params Date: Fri, 26 Jul 2019 09:39:19 -0400 Message-Id: <20190726133936.11177-69-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190726133936.11177-1-sashal@kernel.org> References: <20190726133936.11177-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Denis Efremov [ Upstream commit f3554aeb991214cbfafd17d55e2bfddb50282e32 ] This fixes a divide by zero error in the setup_format_params function of the floppy driver. Two consecutive ioctls can trigger the bug: The first one should set the drive geometry with such .sect and .rate values for the F_SECT_PER_TRACK to become zero. Next, the floppy format operation should be called. A floppy disk is not required to be inserted. An unprivileged user could trigger the bug if the device is accessible. The patch checks F_SECT_PER_TRACK for a non-zero value in the set_geometry function. The proper check should involve a reasonable upper limit for the .sect and .rate fields, but it could change the UAPI. The patch also checks F_SECT_PER_TRACK in the setup_format_params, and cancels the formatting operation in case of zero. The bug was found by syzkaller. Signed-off-by: Denis Efremov Tested-by: Willy Tarreau Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- drivers/block/floppy.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c index 9fb9b312ab6b..51246bc9709a 100644 --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -2120,6 +2120,9 @@ static void setup_format_params(int track) raw_cmd->kernel_data = floppy_track_buffer; raw_cmd->length = 4 * F_SECT_PER_TRACK; + if (!F_SECT_PER_TRACK) + return; + /* allow for about 30ms for data transport per track */ head_shift = (F_SECT_PER_TRACK + 5) / 6; @@ -3232,6 +3235,8 @@ static int set_geometry(unsigned int cmd, struct floppy_struct *g, /* sanity checking for parameters. */ if (g->sect <= 0 || g->head <= 0 || + /* check for zero in F_SECT_PER_TRACK */ + (unsigned char)((g->sect << 2) >> FD_SIZECODE(g)) == 0 || g->track <= 0 || g->track > UDP->tracks >> STRETCH(g) || /* check if reserved bits are set */ (g->stretch & ~(FD_STRETCH | FD_SWAPSIDES | FD_SECTBASEMASK)) != 0) -- 2.20.1