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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2021-09-07 20:00:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-09-08 11:50:27 -0700
commitb234ed6d629420827e2839c8c8935be85a0867fd (patch)
tree766b0b08ea497f6d66914392ef3749197afffbd3 /init/initramfs.c
parent1e1c15839df084f4011825fee922aa976c9159dc (diff)
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 <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>
Diffstat (limited to 'init/initramfs.c')
-rw-r--r--init/initramfs.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/init/initramfs.c b/init/initramfs.c
index af27abc59643..a842c0544745 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -15,6 +15,7 @@
#include <linux/mm.h>
#include <linux/namei.h>
#include <linux/init_syscalls.h>
+#include <linux/umh.h>
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;