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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 commite7cb072eb9("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:e7cb072eb9("init/initramfs.c: do unpacking asynchronously") Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Reported-by: Alexander Egorenkov <egorenar@linux.ibm.com> Reported-by: Bruno Goncalves <bgoncalv@redhat.com> Reported-by: Heiner Kallweit <hkallweit1@gmail.com> Cc: Luis Chamberlain <mcgrof@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
42 lines
862 B
C
42 lines
862 B
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* init/noinitramfs.c
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*
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* Copyright (C) 2006, NXP Semiconductors, All Rights Reserved
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* Author: Jean-Paul Saman <jean-paul.saman@nxp.com>
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*/
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#include <linux/init.h>
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#include <linux/stat.h>
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#include <linux/kdev_t.h>
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#include <linux/syscalls.h>
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#include <linux/init_syscalls.h>
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#include <linux/umh.h>
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/*
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* Create a simple rootfs that is similar to the default initramfs
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*/
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static int __init default_rootfs(void)
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{
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int err;
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usermodehelper_enable();
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err = init_mkdir("/dev", 0755);
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if (err < 0)
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goto out;
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err = init_mknod("/dev/console", S_IFCHR | S_IRUSR | S_IWUSR,
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new_encode_dev(MKDEV(5, 1)));
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if (err < 0)
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goto out;
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err = init_mkdir("/root", 0700);
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if (err < 0)
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goto out;
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return 0;
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out:
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printk(KERN_WARNING "Failed to create a rootfs\n");
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return err;
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}
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rootfs_initcall(default_rootfs);
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