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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 EB4C7C4167B for ; Mon, 13 Sep 2021 14:29:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E09B260F58 for ; Mon, 13 Sep 2021 14:29:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241416AbhIMOao (ORCPT ); Mon, 13 Sep 2021 10:30:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:46952 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345453AbhIMO0c (ORCPT ); Mon, 13 Sep 2021 10:26:32 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5B1C861B5F; Mon, 13 Sep 2021 13:49:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1631540943; bh=p8yyQc5/4w+JVWmWQWdhpaKX6u20yEqXCmCwgkXq114=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xjpxf6tjo7bBwQm0kioNjXuWX53DOgpNKLpTwRiQScJ0FuC9YQDZXuWBHqNPYWHw6 bcg9htcxcWCOhZVXRbNxQqEcqYSh4+Qr/Yd//Lej7arqzhj6mAEPkDyfipOUAyWLcD 3JR0eD3zhoFFXpFoXvzV6GmsqBYlEZYfCu2Ked5A= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+9937dc42271cd87d4b98@syzkaller.appspotmail.com, Christoph Hellwig , Pavel Skripkin , Jens Axboe , Sasha Levin Subject: [PATCH 5.14 066/334] block: nbd: add sanity check for first_minor Date: Mon, 13 Sep 2021 15:12:00 +0200 Message-Id: <20210913131115.641480769@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210913131113.390368911@linuxfoundation.org> References: <20210913131113.390368911@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Pavel Skripkin [ Upstream commit b1a811633f7321cf1ae2bb76a66805b7720e44c9 ] Syzbot hit WARNING in internal_create_group(). The problem was in too big disk->first_minor. disk->first_minor is initialized by value, which comes from userspace and there wasn't any sanity checks about value correctness. It can cause duplicate creation of sysfs files/links, because disk->first_minor will be passed to MKDEV() which causes truncation to byte. Since maximum minor value is 0xff, let's check if first_minor is correct minor number. NOTE: the root case of the reported warning was in wrong error handling in register_disk(), but we can avoid passing knowingly wrong values to sysfs API, because sysfs error messages can confuse users. For example: user passed 1048576 as index, but sysfs complains about duplicate creation of /dev/block/43:0. It's not obvious how 1048576 becomes 0. Log and reproducer for above example can be found on syzkaller bug report page. Link: https://syzkaller.appspot.com/bug?id=03c2ae9146416edf811958d5fd7acfab75b143d1 Fixes: b0d9111a2d53 ("nbd: use an idr to keep track of nbd devices") Reported-by: syzbot+9937dc42271cd87d4b98@syzkaller.appspotmail.com Reviewed-by: Christoph Hellwig Signed-off-by: Pavel Skripkin Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- drivers/block/nbd.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 7ed888e99f09..93708b1938e8 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1770,7 +1770,17 @@ static int nbd_dev_add(int index) refcount_set(&nbd->refs, 1); INIT_LIST_HEAD(&nbd->list); disk->major = NBD_MAJOR; + + /* Too big first_minor can cause duplicate creation of + * sysfs files/links, since first_minor will be truncated to + * byte in __device_add_disk(). + */ disk->first_minor = index << part_shift; + if (disk->first_minor > 0xff) { + err = -EINVAL; + goto out_free_idr; + } + disk->minors = 1 << part_shift; disk->fops = &nbd_fops; disk->private_data = nbd; -- 2.30.2