From: Jessica Yu jeyu@kernel.org
stable inclusion from linux-4.19.165 commit 74925430503eccee4ddf20f3b46a580ca6a72bab
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[ Upstream commit 38dc717e97153e46375ee21797aa54777e5498f3 ]
Apparently there has been a longstanding race between udev/systemd and the module loader. Currently, the module loader sends a uevent right after sysfs initialization, but before the module calls its init function. However, some udev rules expect that the module has initialized already upon receiving the uevent.
This race has been triggered recently (see link in references) in some systemd mount unit files. For instance, the configfs module creates the /sys/kernel/config mount point in its init function, however the module loader issues the uevent before this happens. sys-kernel-config.mount expects to be able to mount /sys/kernel/config upon receipt of the module loading uevent, but if the configfs module has not called its init function yet, then this directory will not exist and the mount unit fails. A similar situation exists for sys-fs-fuse-connections.mount, as the fuse sysfs mount point is created during the fuse module's init function. If udev is faster than module initialization then the mount unit would fail in a similar fashion.
To fix this race, delay the module KOBJ_ADD uevent until after the module has finished calling its init routine.
References: https://github.com/systemd/systemd/issues/17586 Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Tested-By: Nicolas Morey-Chaisemartin nmoreychaisemartin@suse.com Signed-off-by: Jessica Yu jeyu@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.com --- kernel/module.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/module.c b/kernel/module.c index 5aa79d8e79ed..820b8e134a71 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -1788,7 +1788,6 @@ static int mod_sysfs_init(struct module *mod) if (err) mod_kobject_put(mod);
- /* delay uevent until full sysfs population */ out: return err; } @@ -1825,7 +1824,6 @@ static int mod_sysfs_setup(struct module *mod, add_sect_attrs(mod, info); add_notes_attrs(mod, info);
- kobject_uevent(&mod->mkobj.kobj, KOBJ_ADD); return 0;
out_unreg_modinfo_attrs: @@ -3495,6 +3493,9 @@ static noinline int do_init_module(struct module *mod) blocking_notifier_call_chain(&module_notify_list, MODULE_STATE_LIVE, mod);
+ /* Delay uevent until module has finished its init routine */ + kobject_uevent(&mod->mkobj.kobj, KOBJ_ADD); + /* * We need to finish all async code before the module init sequence * is done. This has potential to deadlock. For example, a newly