From patchwork Tue Sep 1 15:08:24 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 310286 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=-13.0 required=3.0 tests=BAYES_00,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=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 695EEC433E7 for ; Tue, 1 Sep 2020 16:45:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 42E602067C for ; Tue, 1 Sep 2020 16:45:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598978721; bh=ps+HJouMxS0MKhtsq4HA6ltIRrGt1y5G3/30b95tvho=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=DU+XVOzKRmG+aNgarC5EpvbddtvwQGDOJCVIa8wx3fPz3OI2g9uKho9bO9LPiumiR Gj/2MwjqcWw+/+mAxN9pEwE6SWIFHZaVUEu9FoGO+KwUPq4bP9lvr2qjqASYodjF+V eKbCbywW3hxxEO2oVPfMcUXAbmyO5/4RyB+hQE5Q= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730213AbgIAQpO (ORCPT ); Tue, 1 Sep 2020 12:45:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:54542 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730202AbgIAP1a (ORCPT ); Tue, 1 Sep 2020 11:27:30 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 BBAE520684; Tue, 1 Sep 2020 15:27:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598974050; bh=ps+HJouMxS0MKhtsq4HA6ltIRrGt1y5G3/30b95tvho=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GfDlJzRCdvuIzg1t/QIHgkNHVVFSrMjP0cg/NHqRyKcbPpeN0YGFTH9JWkhbUA3wT BvvhH8zlu7T5qZxOSJXQMv/AsXE3EeH80q+I5M0Q5wcSr9dgxnP72PMlqXn2Cz2g7f VsdEc8YNQGcqo/0P3fhE1zLkuv7VgesVQ3radtDU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Luis Chamberlain , Christoph Hellwig , Bart Van Assche , Jens Axboe , Sasha Levin Subject: [PATCH 5.4 024/214] blktrace: ensure our debugfs dir exists Date: Tue, 1 Sep 2020 17:08:24 +0200 Message-Id: <20200901150954.130300809@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200901150952.963606936@linuxfoundation.org> References: <20200901150952.963606936@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Luis Chamberlain [ Upstream commit b431ef837e3374da0db8ff6683170359aaa0859c ] We make an assumption that a debugfs directory exists, but since this can fail ensure it exists before allowing blktrace setup to complete. Otherwise we end up stuffing blktrace files on the debugfs root directory. In the worst case scenario this *in theory* can create an eventual panic *iff* in the future a similarly named file is created prior on the debugfs root directory. This theoretical crash can happen due to a recursive removal followed by a specific dentry removal. This doesn't fix any known crash, however I have seen the files go into the main debugfs root directory in cases where the debugfs directory was not created due to other internal bugs with blktrace now fixed. blktrace is also completely useless without this directory, so this ensures to userspace we only setup blktrace if the kernel can stuff files where they are supposed to go into. debugfs directory creations typically aren't checked for, and we have maintainers doing sweep removals of these checks, but since we need this check to ensure proper userspace blktrace functionality we make sure to annotate the justification for the check. Signed-off-by: Luis Chamberlain Reviewed-by: Christoph Hellwig Reviewed-by: Bart Van Assche Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- kernel/trace/blktrace.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index a4c8f9d9522e4..884333b9fc767 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -535,6 +535,18 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev, #endif bt->dir = dir = debugfs_create_dir(buts->name, blk_debugfs_root); + /* + * As blktrace relies on debugfs for its interface the debugfs directory + * is required, contrary to the usual mantra of not checking for debugfs + * files or directories. + */ + if (IS_ERR_OR_NULL(dir)) { + pr_warn("debugfs_dir not present for %s so skipping\n", + buts->name); + ret = -ENOENT; + goto err; + } + bt->dev = dev; atomic_set(&bt->dropped, 0); INIT_LIST_HEAD(&bt->running_list);