linux-kernel - [PATCH] ftrace/module: Call clean up function when module init fails early

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Message-ID: <20160105210506.6a208153@gandalf.local.home>
Date:	Tue, 5 Jan 2016 21:05:06 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	"Qiu, PeiyangX" <peiyangx.qiu@...el.com>
Subject: [PATCH] ftrace/module: Call clean up function when module init
 fails early


[ Rusty, I'm currently testing this patch. Can you give me an Acked-by? ]

If the module init code fails after calling ftrace_module_init() and before
calling do_init_module(), we can suffer from a memory leak. This is because
ftrace_module_init() allocates pages to store the locations that ftrace
hooks are placed in the module text. If do_init_module() fails, it still
calls the MODULE_GOING notifiers which will tell ftrace to do a clean up of
the pages it allocated for the module. But if load_module() fails before
then, the pages allocated by ftrace_module_init() will never be freed.

Call ftrace_release_mod() on the module if load_module() fails before
getting to do_init_module().

Link: http://lkml.kernel.org/r/567CEA31.1070507@intel.com

Reported-by: "Qiu, PeiyangX" <peiyangx.qiu@...el.com>
Fixes: a949ae560a511 "ftrace/module: Hardcode ftrace_module_init() call into load_module()"
Cc: stable@...r.kernel.org # v2.6.38+
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 kernel/module.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/module.c b/kernel/module.c
index 8f051a106676..38c7bd5583ff 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3571,6 +3571,12 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	synchronize_sched();
 	mutex_unlock(&module_mutex);
  free_module:
+	/*
+	 * Ftrace needs to clean up what it initialized.
+	 * This does nothing if ftrace_module_init() wasn't called,
+	 * but it must be called outside of module_mutex.
+	 */
+	ftrace_release_mod(mod);
 	/* Free lock-classes; relies on the preceding sync_rcu() */
 	lockdep_free_key_range(mod->module_core, mod->core_size);
 
-- 
1.8.3.1

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