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kernel/module.c: wakeup processes in module_wq on module unload

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[ Upstream commit 5d603311615f612320bb77bd2a82553ef1ced5b7 ]

Fix the race between load and unload a kernel module.

sys_delete_module()
 try_stop_module()
  mod->state = _GOING
					add_unformed_module()
					 old = find_module_all()
					 (old->state == _GOING =>
					  wait_event_interruptible())

					 During pre-condition
					 finished_loading() rets 0
					 schedule()
					 (never gets waken up later)
 free_module()
  mod->state = _UNFORMED
   list_del_rcu(&mod->list)
   (dels mod from "modules" list)

return

The race above leads to modprobe hanging forever on loading
a module.

Error paths on loading module call wake_up_all(&module_wq) after
freeing module, so let's do the same on straight module unload.

Fixes: 6e6de3dee51a ("kernel/module.c: Only return -EEXIST for modules that have finished loading")
Reviewed-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Konstantin Khorenko
2019-11-13 12:29:50 +03:00
committed by Greg Kroah-Hartman
parent 0773dcee66
commit 12c88d91a8
1 changed files with 2 additions and 0 deletions
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2
kernel/module.c
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@@ -1021,6 +1021,8 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
strlcpy(last_unloaded_module, mod->name, sizeof(last_unloaded_module)); strlcpy(last_unloaded_module, mod->name, sizeof(last_unloaded_module));
free_module(mod); free_module(mod);
/* someone could wait for the module in add_unformed_module() */
wake_up_all(&module_wq);
return 0; return 0;
out: out:
mutex_unlock(&module_mutex); mutex_unlock(&module_mutex);