[kernel-hardening] [RFC 3/7] module: modify memory attrs for __ro_mostly_after_init during module_init/exit

Hoeun Ryu
2017-02-19T10:04:06Z

`__ro_mostly_after_init` is almost like `__ro_after_init`. The section is
read-only as same as `__ro_after_init` after kernel init. This patch makes
`__ro_mostly_after_init` section read-write temporarily only during
module_init/module_exit.

Signed-off-by: Hoeun Ryu <hoeun.ryu@gmail.com>
---
kernel/module.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 7eba6de..3b25e0e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -987,8 +987,11 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,

mutex_unlock(&module_mutex);
/* Final destruction now no one is using it. */
- if (mod->exit != NULL)
+ if (mod->exit != NULL) {
+ set_ro_mostly_after_init_rw();
mod->exit();
+ set_ro_mostly_after_init_ro();
+ }
blocking_notifier_call_chain(&module_notify_list,
MODULE_STATE_GOING, mod);
klp_module_going(mod);
@@ -3396,8 +3399,11 @@ static noinline int do_init_module(struct module *mod)

do_mod_ctors(mod);
/* Start the module */
- if (mod->init != NULL)
+ if (mod->init != NULL) {
+ set_ro_mostly_after_init_rw();
ret = do_one_initcall(mod->init);
+ set_ro_mostly_after_init_ro();
+ }
if (ret < 0) {
goto fail_free_freeinit;
}
--
2.7.4