[PATCH 4.2.y-ckt 297/305] ftrace/module: Call clean up function when module init fails early

[Kamal Mostafa]

4.2.8-ckt2 -stable review patch.  If anyone has any objections, please let me know.

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

From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>

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@xxxxxxxxx

Reported-by: "Qiu, PeiyangX" <peiyangx.qiu@xxxxxxxxx>
Fixes: a949ae560a511 "ftrace/module: Hardcode ftrace_module_init() call into load_module()"
Acked-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
 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 6cd8c0e..47420d4 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -575,6 +575,7 @@ 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 8f051a1..38c7bd5 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);
 
-- 
1.9.1