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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 270C2C433EF for ; Wed, 8 Sep 2021 03:00:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 11BA26113C for ; Wed, 8 Sep 2021 03:00:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347291AbhIHDBN (ORCPT ); Tue, 7 Sep 2021 23:01:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:59386 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347404AbhIHDBL (ORCPT ); Tue, 7 Sep 2021 23:01:11 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9F78061100; Wed, 8 Sep 2021 03:00:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1631070004; bh=ClLfEoWecriABwZ5pCobmV4YDStOMst9F8QLyV70exg=; h=Date:From:To:Subject:In-Reply-To:From; b=tnu8IHQ2s3YcLhu93Cthq1+euWgLZ7KqCfSGRWQ1Le8mdvgR238YP4zraUz1SlNag cqBefrvjNN3imLob4cSElQK46MQOl4MRdV44MoBcNVlaanqd19RiEQcrzA0cJT2tzb SsV38b7eanPWOU6j99lvHhkgSMYmrXZEN/8jX/EA= Date: Tue, 07 Sep 2021 20:00:03 -0700 From: Andrew Morton To: akpm@linux-foundation.org, bgoncalv@redhat.com, egorenar@linux.ibm.com, hkallweit1@gmail.com, linux-mm@kvack.org, linux@rasmusvillemoes.dk, mcgrof@kernel.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 128/147] init: move usermodehelper_enable() to populate_rootfs() Message-ID: <20210908030003.WFvhfWzKJ%akpm@linux-foundation.org> In-Reply-To: <20210907195226.14b1d22a07c085b22968b933@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Rasmus Villemoes Subject: init: move usermodehelper_enable() to populate_rootfs() Currently, usermodehelper is enabled right before PID1 starts going through the initcalls. However, any call of a usermodehelper from a pure_, core_, postcore_, arch_, subsys_ or fs_ initcall is futile, as there is no filesystem contents yet. Up until commit e7cb072eb988 ("init/initramfs.c: do unpacking asynchronously"), such calls, whether via some request_module(), a legacy uevent "/sbin/hotplug" notification or something else, would just fail silently with (presumably) -ENOENT from kernel_execve(). However, that commit introduced the wait_for_initramfs() synchronization hook which must be called from the usermodehelper exec path right before the kernel_execve, in order that request_module() et al done from *after* rootfs_initcall() time (i.e. device_ and late_ initcalls) would continue to find a populated initramfs as they used to. Any call of wait_for_initramfs() done before the unpacking has been scheduled (i.e. before rootfs_initcall time) must just return immediately [and let the caller find an empty file system] in order not to deadlock the machine. I mistakenly thought, and my limited testing confirmed, that there were no such calls, so I added a pr_warn_once() in wait_for_initramfs(). It turns out that one can indeed hit request_module() as well as kobject_uevent_env() during those early init calls, leading to a user-visible warning in the kernel log emitted consistently for certain configurations. We could just remove the pr_warn_once(), but I think it's better to postpone enabling the usermodehelper framework until there is at least some chance of finding the executable. That is also a little more efficient in that a lot of work done in umh.c will be elided. However, it does change the error seen by those early callers from -ENOENT to -EBUSY, so there is a risk of a regression if any caller care about the exact error value. Link: https://lkml.kernel.org/r/20210728134638.329060-1-linux@rasmusvillemoes.dk Fixes: e7cb072eb988 ("init/initramfs.c: do unpacking asynchronously") Signed-off-by: Rasmus Villemoes Reported-by: Alexander Egorenkov Reported-by: Bruno Goncalves Reported-by: Heiner Kallweit Cc: Luis Chamberlain Signed-off-by: Andrew Morton --- init/initramfs.c | 2 ++ init/main.c | 1 - init/noinitramfs.c | 2 ++ 3 files changed, 4 insertions(+), 1 deletion(-) --- a/init/initramfs.c~init-move-usermodehelper_enable-to-populate_rootfs +++ a/init/initramfs.c @@ -15,6 +15,7 @@ #include #include #include +#include static ssize_t __init xwrite(struct file *file, const char *p, size_t count, loff_t *pos) @@ -727,6 +728,7 @@ static int __init populate_rootfs(void) { initramfs_cookie = async_schedule_domain(do_populate_rootfs, NULL, &initramfs_domain); + usermodehelper_enable(); if (!initramfs_async) wait_for_initramfs(); return 0; --- a/init/main.c~init-move-usermodehelper_enable-to-populate_rootfs +++ a/init/main.c @@ -1392,7 +1392,6 @@ static void __init do_basic_setup(void) driver_init(); init_irq_proc(); do_ctors(); - usermodehelper_enable(); do_initcalls(); } --- a/init/noinitramfs.c~init-move-usermodehelper_enable-to-populate_rootfs +++ a/init/noinitramfs.c @@ -10,6 +10,7 @@ #include #include #include +#include /* * Create a simple rootfs that is similar to the default initramfs @@ -18,6 +19,7 @@ static int __init default_rootfs(void) { int err; + usermodehelper_enable(); err = init_mkdir("/dev", 0755); if (err < 0) goto out; _