On Mon 2015-05-18 10:22:21, Josh Poimboeuf wrote:
> On Mon, May 18, 2015 at 02:08:06PM +0200, Petr Mladek wrote:
> > On Wed 2015-05-13 09:14:15, Josh Poimboeuf wrote:
> > > On Tue, May 12, 2015 at 10:04:44PM +0800, Minfei Huang wrote:
> > > > @@ -930,6 +932,7 @@ disabled:
> > > > static int klp_module_notify(struct notifier_block *nb, unsigned long
> > > > action,
> > > > void *data)
> > > > {
> > > > + int ret;
> > > > struct module *mod = data;
> > > > struct klp_patch *patch;
> > > > struct klp_object *obj;
> > > > @@ -955,7 +958,13 @@ static int klp_module_notify(struct notifier_block
> > > > *nb, unsigned long action,
> > > >
> > > > if (action == MODULE_STATE_COMING) {
> > > > obj->mod = mod;
> > > > - klp_module_notify_coming(patch, obj);
> > > > + ret = klp_module_notify_coming(patch,
> > > > obj);
> > > > + if (ret) {
> > > > + obj->mod = NULL;
> > > > + pr_warn("patch '%s' is dead,
> > > > remove it "
> > > > + "or re-install the
> > > > module '%s'\n",
> > > > + patch->mod->name,
> > > > obj->name);
> > > > + }
> > >
> > > The patch isn't necessarily dead, since it might also include previously
> > > enabled changes for vmlinux or other modules. It can actually be a
> > > dangerous condition if there's a mismatch between old code in the module
> > > and new code elsewhere. How about something like:
> > >
> > > "patch '%s' is in an inconsistent state!\n"
> >
> > It must not be dangerous, otherwise the patch could not get applied
> > immediately.
> >
> > I would omit this message completely. It would just duplicate the
> > warning printed by klp_module_notify_coming().
>
> This error path doesn't mean that the entire patch isn't applied. It
> only affects the subset of the patch which applies to the coming module.
> So you can have a dangerous mismatch in the case of a patch which
> patches multiple objects.
We apply the patch immediately. This simple consistency model allows
to call patched function from an upatched one and vice versa. It means
that there must _not_ be any dependency between patched functions.
And it means that it must be safe to keep the module unpatched.
The situation will change after we introduce a more complex
consistency model. Then we will need to patch the module
directly in load_module() and refuse loading in case of error.
By other words, we will not and must not allow any dangerous state.
Does it make sense? Or did I miss anything, please?
Best Regards,
Petr
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