From patchwork Tue Sep 1 15:09:32 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: 264797 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=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 7ABFCC433E6 for ; Tue, 1 Sep 2020 15:21:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51076206FA for ; Tue, 1 Sep 2020 15:21:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598973717; bh=tVS2ZQ+Ws0jCOq4RwVouKorzH4DD8uDRN4VgE2azIpw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Vr8N+VzvWxaJCvneo/Oq68SmHrh/3S00JitRC9PlzDnspFZ4dGg0fHOgEpoka0TVe QW8JeACLGE0HR/RtaPERYn1Iif0PI3OWW1XvjFsjk72kVk/4qBsBtjhxFVyaWwjLmY ZthdlyXtUwE1pdgkOrKysgjRnd+KmK4I53CdMFXk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728732AbgIAPVz (ORCPT ); Tue, 1 Sep 2020 11:21:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:42962 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729154AbgIAPVx (ORCPT ); Tue, 1 Sep 2020 11:21:53 -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 3F64D20BED; Tue, 1 Sep 2020 15:21:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598973712; bh=tVS2ZQ+Ws0jCOq4RwVouKorzH4DD8uDRN4VgE2azIpw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gAzbxd/Ar9W1DejTQAF2YQE5zG7ExDbZRfAFAR+rmtJjWQTiuu7/MFJ8oltp50RKG hjcBHJi379HWzMKy10b4UykI9AplbPJtCdVABvoKFpXMRL9gqW+hs6da4JF9rReEFH QfISuZb4/UssaYhQ1/5bQM7p+iHRTjxClox56DgU= 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 4.19 017/125] blktrace: ensure our debugfs dir exists Date: Tue, 1 Sep 2020 17:09:32 +0200 Message-Id: <20200901150935.417995417@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200901150934.576210879@linuxfoundation.org> References: <20200901150934.576210879@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 7a4ca2deb39bc..1442f6152abc2 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -529,6 +529,18 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev, if (!dir) goto err; + /* + * 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);