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 24A73C7618B for ; Fri, 26 Jul 2019 13:47:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F32AA22CE5 for ; Fri, 26 Jul 2019 13:47:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564148826; bh=IKqPvwO/J1gl0Te7r7i+nqmrap3Pg4zpB7nnpfushCM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Pin8Dy7jqExY4EYzQY7hb9o3SWnWDQXIzAIuI59eMd4pHiXwRTn3itNZkIsRWMkvd w64+hLRbZaAYk7qOarjecb5+02jNiQ4RBnOLZEAD/fvTcN3HFd2FuoWEPiRuFOltLs cZgIryuyf51hjdwO8e4qyGEOA2GhKkGcoiXn6K/8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388733AbfGZNrE (ORCPT ); Fri, 26 Jul 2019 09:47:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:55504 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727301AbfGZNqH (ORCPT ); Fri, 26 Jul 2019 09:46:07 -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 7091D22CD8; Fri, 26 Jul 2019 13:46:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564148766; bh=IKqPvwO/J1gl0Te7r7i+nqmrap3Pg4zpB7nnpfushCM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CDclx+L6pi74KKVLZjdXUjdq75APytQjtckNTSXYsFypU1r1xAJ7wh0MBcie6Zfjn 2giEYzLEsxO+qgNQN4yg7hBLm8RLw/kFGD/7DeM7WvL09PB5lARUQgVYRERQmglPMn rty72j99r08bUScR8tZzrk0y85T5vZIcOrHYJdrA= 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 4.4 21/23] floppy: fix div-by-zero in setup_format_params Date: Fri, 26 Jul 2019 09:45:20 -0400 Message-Id: <20190726134522.13308-21-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190726134522.13308-1-sashal@kernel.org> References: <20190726134522.13308-1-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 2daa5b84abbc..42ae1d2d8243 100644 --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -2113,6 +2113,9 @@ 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; @@ -3235,6 +3238,8 @@ 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