Steven Rostedt <rost...@goodmis.org> writes:
> On Mon, 24 Mar 2014 20:26:05 +0900
> Masami Hiramatsu <masami.hiramatsu...@hitachi.com> wrote:
>
>
>> Thank you for reporting with this pretty backtrace :)
>> Steven, I think this is not the kprobe bug but ftrace (and perhaps, module).
>
> Looks to be more of a module issue than a ftrace issue.
>
>>
>> If the ftrace can set loading module text read only before the module
>> subsystem
>> expected, I think it should be protected by the module subsystem itself
>> (e.g. set_all_modules_text_ro(rw) skips the modules which is
>> MODULE_STATE_COMING)
>>
>
> Does this patch fix it?
>
> In-review-off-by: Steven Rostedt <rost...@goodmis.org>
Sorry, was on paternity leave.
I'm always nervous about adding more states, since every place which
examines the state has to be audited.
We set the mod->state to MOD_STATE_COMING in complete_formation;
why don't we set NX there instead? It also makes more sense to
set NX before we hit parse_args() which can execute code in the module.
In fact, we should probably call the notifier there too, so people
can breakpoint/tracepoint/etc parameter calls.
Of course, this means that we set NX before the notifier; does anything
break?
Subject: module: set nx before marking module MODULE_STATE_COMING.
This prevents a WARN_ON() where ftrace calls set_all_modules_text_ro()
which races with the module setting its own set_section_ro_nx().
It also means we're NX protected before we call parse_args(), which
can execute module code.
This means that the notifiers will be called on a module which
is already NX, so that may cause problems.
Signed-off-by: Rusty Russell <ru...@rustcorp.com.au>
diff --git a/kernel/module.c b/kernel/module.c
index 11869408f79b..83a437e5d429 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3023,21 +3023,6 @@ static int do_init_module(struct module *mod)
*/
current->flags &= ~PF_USED_ASYNC;
- blocking_notifier_call_chain(&module_notify_list,
- MODULE_STATE_COMING, mod);
-
- /* Set RO and NX regions for core */
- set_section_ro_nx(mod->module_core,
- mod->core_text_size,
- mod->core_ro_size,
- mod->core_size);
-
- /* Set RO and NX regions for init */
- set_section_ro_nx(mod->module_init,
- mod->init_text_size,
- mod->init_ro_size,
- mod->init_size);
-
do_mod_ctors(mod);
/* Start the module */
if (mod->init != NULL)
@@ -3168,9 +3153,26 @@ static int complete_formation(struct module *mod, struct
load_info *info)
/* This relies on module_mutex for list integrity. */
module_bug_finalize(info->hdr, info->sechdrs, mod);
+ /* Set RO and NX regions for core */
+ set_section_ro_nx(mod->module_core,
+ mod->core_text_size,
+ mod->core_ro_size,
+ mod->core_size);
+
+ /* Set RO and NX regions for init */
+ set_section_ro_nx(mod->module_init,
+ mod->init_text_size,
+ mod->init_ro_size,
+ mod->init_size);
+
/* Mark state as coming so strong_try_module_get() ignores us,
* but kallsyms etc. can see us. */
mod->state = MODULE_STATE_COMING;
+ mutex_unlock(&module_mutex);
+
+ blocking_notifier_call_chain(&module_notify_list,
+ MODULE_STATE_COMING, mod);
+ return 0;
out:
mutex_unlock(&module_mutex);
--
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