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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 45987C4338F for ; Thu, 12 Aug 2021 09:15:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 19DDD60F00 for ; Thu, 12 Aug 2021 09:15:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235732AbhHLJPh (ORCPT ); Thu, 12 Aug 2021 05:15:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60578 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234895AbhHLJPe (ORCPT ); Thu, 12 Aug 2021 05:15:34 -0400 Received: from mail-lf1-x132.google.com (mail-lf1-x132.google.com [IPv6:2a00:1450:4864:20::132]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E7DAC0613D5; Thu, 12 Aug 2021 02:15:08 -0700 (PDT) Received: by mail-lf1-x132.google.com with SMTP id x27so12232352lfu.5; Thu, 12 Aug 2021 02:15:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=iNZvgEwzNlv74EhPdPOrR7WRv0hD45zwdbp38WU3FKg=; b=h+hLzT97yAPBswp6hlz/ItmWV82FKo/j+KipuGYmmIkHRfMdCpQ4nRsjYf/G2s4IUg vqOnTqFl99HsyPm7PSqdTBXXD92aSpv/v99/qAlIHe/lwu7BiqG5hQKEej6P/b0T2NV4 Udz6ivLrGOfK56DTIbmUd174WN8GtlnNBbxR8orB/XeIqCVgK3TtdHqCZ5GJr2LfmMCD 7A6Wa7loVfIzoBSBXoYU7AHWix5PR28hudeN7AAJZIAZB5SBuDT52j8hI9mgDGC98C4j x9lIik0UvW9/+8AOxMk5NPWf6yTiSD1k8xc8iWBNi219thpwwFED9gL5D5F7jv8jnqKq hTZA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=iNZvgEwzNlv74EhPdPOrR7WRv0hD45zwdbp38WU3FKg=; b=OaTMlvSpX+AlBHKCuQbzxdQpBIb1fCH0etR3FLO83SoHY7/fMKAgeaKv9fUOZRxBLz lcMCD3WuhvKcgGRYM7mvldYgN6+Ewurjrg0x2+wb7kg0cqNR3C3GKpgLm+O1M5Tz7uB6 Nzlf52VOvyBPMvg2MnEDHpAIjZS8ZflS+D0IiznnhtS3DFg3LpSSLvaaKWSyCG69t6xM SEpZabaSl8x9aKoLrPqdQX8+dX54xeP8mDjiLhz+ABar0O5jwNlzLvcB09oj5mRo2usi pzBrN42wxKkGigstnJ/Bqb8jA43Wsw6vvC3nAejPYCJp6g1D29m8kKP/Q5NxeCXdidsY +bnQ== X-Gm-Message-State: AOAM530WfC9Couhl5wm1B5mdgyZ+v3n1xu+E7eP/PTNASrxGHOrqd5rk Z823s8c52GxjHEWJfrEGsdc= X-Google-Smtp-Source: ABdhPJxVB+cmqliIX3pFzzoc6Q63jgJhn4JTxvzkGi0+AkKwc7iI4rwUk/r3BxhQZ79Dfg7ticWITQ== X-Received: by 2002:ac2:4e8c:: with SMTP id o12mr1925327lfr.374.1628759706519; Thu, 12 Aug 2021 02:15:06 -0700 (PDT) Received: from localhost.localdomain ([46.235.67.232]) by smtp.gmail.com with ESMTPSA id q66sm246264ljb.83.2021.08.12.02.15.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Aug 2021 02:15:06 -0700 (PDT) From: Pavel Skripkin To: josef@toxicpanda.com, axboe@kernel.dk Cc: hch@lst.de, linux-block@vger.kernel.org, nbd@other.debian.org, linux-kernel@vger.kernel.org, Pavel Skripkin , syzbot+9937dc42271cd87d4b98@syzkaller.appspotmail.com Subject: [PATCH] block: nbd: add sanity check for first_minor Date: Thu, 12 Aug 2021 12:15:01 +0300 Message-Id: <20210812091501.22648-1-paskripkin@gmail.com> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Signed-off-by: Pavel Skripkin --- drivers/block/nbd.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index c38317979f74..600e9bab5d43 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1725,7 +1725,17 @@ 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; -- 2.32.0