linux-kernel - [PATCH v2 1/5] module: Wait for RCU synchronizing before releasing a module

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Date:	Thu, 23 Oct 2014 15:26:43 -0400
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Lucas De Marchi <lucas.demarchi@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>
Subject: [PATCH v2 1/5] 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@...achi.com>
---
 kernel/module.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/module.c b/kernel/module.c
index 88cec1d..331b03f 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);


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