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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 7B4E0C76186 for ; Wed, 24 Jul 2019 19:34:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4ECBE229F3 for ; Wed, 24 Jul 2019 19:34:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563996889; bh=Nkas8Jif7pWemiGlAUKYyku8WRki+sdH/VZpZLAoFuw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=NcK+h9/TrwSqnWHNsRkirF77V5czs4GUUP9w4TCgrrKJA4TcOVzaYhNVng6hTuKNM WlpLekm2m2IlTtxRwYkOyQTDPr9VcwnliQQa0RW6v0W2OhcTxcRZLQI1JJE3Z31lt8 0CJ/k1n5nmTx/liSjxpMStx9bjukCoogfu7q62HQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389117AbfGXTes (ORCPT ); Wed, 24 Jul 2019 15:34:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:57388 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388566AbfGXTep (ORCPT ); Wed, 24 Jul 2019 15:34:45 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7C8A520659; Wed, 24 Jul 2019 19:34:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563996885; bh=Nkas8Jif7pWemiGlAUKYyku8WRki+sdH/VZpZLAoFuw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JlRI4dPUfn9Waioctaovko/17KsxG+8jHOAhlrwhILX0HBcf94Zk2SJGx0oJYxBO3 kzWkIaC23kqQUJnZjmySwnc1naTxDF+BEWtht4DfVgESOF3LH9BMRfa7MDKuPvLYok XbGOCVGKOsVGdl2F4wQEsrBKqEGYmVblBRSdMGoE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Denis Efremov , Willy Tarreau , Linus Torvalds , Sasha Levin Subject: [PATCH 5.2 248/413] floppy: fix div-by-zero in setup_format_params Date: Wed, 24 Jul 2019 21:18:59 +0200 Message-Id: <20190724191753.333671252@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190724191735.096702571@linuxfoundation.org> References: <20190724191735.096702571@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ 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