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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 C0A11C433E1 for ; Fri, 21 Aug 2020 16:23:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9CC4E206DA for ; Fri, 21 Aug 2020 16:23:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598027021; bh=l58UeMdt58IB+x76B7v0N/wZQsYhLLAl8Lj5oZQQp3c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=PBQatWh3UJtbHOVyUsJHZ5IgAAJwNvCegVnWo1y1fmElKcHZ+zAo7R5LjfvDDP8wH d3MTXw1hnOie3U7ppL+63frwcZDszfBU+0fqMGcq+nm5dX5CogOqLrVhQE2+LWzAzi VuIaCk2hyN7CVBjOjJhkx/Zqus3hzDifJtaF+dk4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728412AbgHUQXg (ORCPT ); Fri, 21 Aug 2020 12:23:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:50212 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728352AbgHUQUF (ORCPT ); Fri, 21 Aug 2020 12:20:05 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2134122CB2; Fri, 21 Aug 2020 16:19:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598026747; bh=l58UeMdt58IB+x76B7v0N/wZQsYhLLAl8Lj5oZQQp3c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Fz3U/iPFEe5tePf5EQ/dIbJMzQVsnU47eMgPPkVHV+er5wjv3uKz85Z1cX4SiSaX+ dElbn3CoexQ97iUIztQq8pj3LSF/dzKVgS4Sx9TjY26LVVWpOjmaGHp+7OFXT51pT1 EHFpVy9JQ8t/4U5qGBHBd5tqwlFEp7ooJmFIqrGQ= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Luis Chamberlain , Christoph Hellwig , Bart Van Assche , Jens Axboe , Sasha Levin , linux-block@vger.kernel.org Subject: [PATCH AUTOSEL 4.14 07/30] blktrace: ensure our debugfs dir exists Date: Fri, 21 Aug 2020 12:18:34 -0400 Message-Id: <20200821161857.348955-7-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200821161857.348955-1-sashal@kernel.org> References: <20200821161857.348955-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 9a55c5bc52434..987daf9cc6e54 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -541,6 +541,18 @@ 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); -- 2.25.1