[PATCH 3.16.y-ckt 121/128] ftrace/module: Call clean up function when module init fails early

[Luis Henriques]

3.16.7-ckt23 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: "Steven Rostedt (Red Hat)" <rostedt at goodmis.org>

commit 049fb9bd416077b3622d317a45796be4f2431df3 upstream.

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 at intel.com>
Fixes: a949ae560a511 "ftrace/module: Hardcode ftrace_module_init() call into load_module()"
Acked-by: Rusty Russell <rusty at rustcorp.com.au>
Signed-off-by: Steven Rostedt <rostedt at goodmis.org>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 include/linux/ftrace.h | 1 +
 kernel/module.c        | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 721de254ba7a..c314fe2e0f46 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -541,6 +541,7 @@ extern int ftrace_arch_read_dyn_info(char *buf, int size);
 
 extern int skip_trace(unsigned long ip);
 extern void ftrace_module_init(struct module *mod);
+extern void ftrace_release_mod(struct module *mod);
 
 extern void ftrace_disable_daemon(void);
 extern void ftrace_enable_daemon(void);
diff --git a/kernel/module.c b/kernel/module.c
index ed4d3b7ec58a..365b0a9d87b3 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3339,6 +3339,12 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	wake_up_all(&module_wq);
 	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);
 	module_deallocate(mod, info);
  free_copy:
 	free_copy(info);