From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Date: Sun, 9 Nov 2014 22:56:29 +0000 (+1030)
Subject: module: Wait for RCU synchronizing before releasing a module
X-Git-Tag: firefly_0821_release~176^2~2623^2~7
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4f48795b6154852d07d971e402c35ecc460ddcb6;p=firefly-linux-kernel-4.4.55.git

module: Wait for RCU synchronizing before releasing a module

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>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---

diff --git a/kernel/module.c b/kernel/module.c
index 88cec1ddb1e3..331b03f6b411 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3326,6 +3326,8 @@ 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);