From b234ed6d629420827e2839c8c8935be85a0867fd Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Tue, 7 Sep 2021 20:00:03 -0700 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 Signed-off-by: Linus Torvalds --- init/noinitramfs.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'init/noinitramfs.c') diff --git a/init/noinitramfs.c b/init/noinitramfs.c index 3d62b07f3bb9..d1d26b93d25c 100644 --- a/init/noinitramfs.c +++ b/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; -- cgit v1.2.3