[RFC PATCH 1/5] module: Wait for RCU synchronizing before releasing a module

[Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>]

Wait for RCU synchronizing on failure path of module loading
before releasing struct module, because the memory of mod->list
can still be accessed by list walkers (e.g. kallsyms).

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
---
 kernel/module.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/module.c b/kernel/module.c
index 03214bd2..4c8a4f1 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3324,6 +3324,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	/* Unlink carefully: kallsyms could be walking list. */
 	list_del_rcu(&mod->list);
 	wake_up_all(&module_wq);
+	/* Wait for RCU synchronizing before releasing mod->list. */
+	synchronize_rcu();
 	mutex_unlock(&module_mutex);
  free_module:
 	module_deallocate(mod, info);