+++ Petr Mladek [04/02/16 15:39 +0100]:
On Mon 2016-02-01 20:17:36, Jessica Yu wrote:
[ snipped since email is getting long ]
diff --git a/kernel/module.c b/kernel/module.c
index b05d466..71c77ed 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -53,6 +53,7 @@
#include <asm/sections.h>
#include <linux/tracepoint.h>
#include <linux/ftrace.h>
+#include <linux/livepatch.h>
#include <linux/async.h>
#include <linux/percpu.h>
#include <linux/kmemleak.h>
@@ -981,6 +982,7 @@ SYSCALL_DEFINE2(delete_module, const char __user *,
name_user,
mod->exit();
blocking_notifier_call_chain(&module_notify_list,
MODULE_STATE_GOING, mod);
+ klp_module_disable(mod);
ftrace_release_mod(mod);
async_synchronize_full();
@@ -3297,6 +3299,7 @@ fail:
module_put(mod);
blocking_notifier_call_chain(&module_notify_list,
MODULE_STATE_GOING, mod);
+ klp_module_disable(mod);
ftrace_release_mod(mod);
free_module(mod);
wake_up_all(&module_wq);
@@ -3375,6 +3378,10 @@ static int complete_formation(struct module *mod, struct
load_info *info)
mutex_unlock(&module_mutex);
ftrace_module_enable(mod);
+ err = klp_module_enable(mod);
+ if (err)
+ goto out;
If you go out here, you need to revert some some operations
that are normally done in the bug_cleanup: goto target
in load_module(). In particular, you need to do:
/* module_bug_cleanup needs module_mutex protection */
mutex_lock(&module_mutex);
module_bug_cleanup(mod);
mutex_unlock(&module_mutex);
ftrace_release_mod(mod);
/* we can't deallocate the module until we clear memory protection */
module_disable_ro(mod);
module_disable_nx(mod);
IMHO, it would make sense to somehow split the complete_formation() function
and avoid a code duplication in the error paths.
Argh, thank you for catching that. I think we could split up
complete_formation()
into two functions in order to make the error handling work.
We could probably take out the coming notifier calls, ftrace_module_enable(),
and klp_module_enable() out of complete_formation(), and put them in another
function, maybe called prepare_coming_module(), that would be called right
after complete_formation(). It might look something like this:
@@ -3614,6 +3621,9 @@ static int load_module(struct load_info *info, const char
__user *uargs,
err = complete_formation(mod, info);
if (err)
goto ddebug_cleanup;
+ err = prepare_coming_module(mod); // calls ftrace_module_enable(),
klp_module_enable(), then coming notifiers
+ if (err) // means that klp_module_enable failed
+ goto bug_cleanup;
/* Module is ready to execute: parsing args may do that. */
after_dashes = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,
@@ -3621,7 +3631,7 @@ static int load_module(struct load_info *info, const char
__user *uargs,
unknown_module_param_cb);
if (IS_ERR(after_dashes)) {
err = PTR_ERR(after_dashes);
- goto bug_cleanup;
+ goto coming_cleanup;
} else if (after_dashes) {
pr_warn("%s: parameters '%s' after `--' ignored\n",
mod->name, after_dashes);
Now for the error conditions. If complete_formation() fails, goto
ddebug_cleanup. If prepare_coming_module() fails (at that point,
module_enable_{ro,nx} and module_bug_finalize() have already finished), goto
bug_cleanup. Everything else that fails afterwards (meaning klp_module_enable,
ftrace_module_enable, and the coming notifiers have finished) goto
coming_cleanup. ftrace_release_mod() gets called in the goto free_module label
so we don't have to call it in coming_module.
@@ -3649,16 +3659,16 @@ static int load_module(struct load_info *info, const
char __user *uargs,
+ coming_cleanup:
+ blocking_notifier_call_chain(&module_notify_list,
+ MODULE_STATE_GOING, mod);
+ klp_module_disable(mod);
bug_cleanup:
/* module_bug_cleanup needs module_mutex protection */
mutex_lock(&module_mutex);
module_bug_cleanup(mod);
mutex_unlock(&module_mutex);
- blocking_notifier_call_chain(&module_notify_list,
- MODULE_STATE_GOING, mod);
- klp_module_disable(mod);
-
/* we can't deallocate the module until we clear memory protection */
module_disable_ro(mod);
module_disable_nx(mod);
Does all this look ok? Also, one last thing, I noticed that module->state isn't
set to MODULE_STATE_GOING anywhere before the going notifier chain is called in
the bug_cleanup label (I think it is still COMING at that point), so the
klp_module_disable call right afterwards would have bailed out because of that.
To be consistent, shouldn't it be set before the going notifiers are called?
Thanks,
Jessica
