Re: module: s390: keep mod_arch_specific for livepatch modules

[Jessica Yu]

+++ Miroslav Benes [16/12/15 13:02 +0100]:
> On Mon, 30 Nov 2015, Jessica Yu wrote:
>
> > Livepatch needs to utilize the symbol information contained in the
> > mod_arch_specific struct in order to be able to call the s390
> > apply_relocate_add() function to apply relocations. Remove the redundant
> > vfree() in module_finalize() since module_arch_freeing_init() (which also frees
> > said structures) is called in do_init_module(). Keep a reference to syminfo if
> > the module is a livepatch module and free the structures in
> > module_arch_cleanup(). If the module isn't a livepatch module, we free the
> > structures in module_arch_freeing_init() as usual.
> >
> > Signed-off-by: Jessica Yu <jeyu@xxxxxxxxxx>
> > ---
> >  arch/s390/kernel/module.c | 13 +++++++++++--
> >  1 file changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
> > index 0c1a679..17a1979 100644
> > --- a/arch/s390/kernel/module.c
> > +++ b/arch/s390/kernel/module.c
> > @@ -51,6 +51,9 @@ void *module_alloc(unsigned long size)
> >
> >  void module_arch_freeing_init(struct module *mod)
> >  {
> > +	if (mod->klp)
> > +		return;
> > +
> >  	vfree(mod->arch.syminfo);
> >  	mod->arch.syminfo = NULL;
> >  }
>
> Hm, this is problematic. module_arch_freeing_init() is called from
> module_deallocate() and this is called in the error path in load_module().
> So if there was an error during load_module() of livepatch module which
> led to free_modinfo label or behind mod->arch.syminfo would not be freed
> at all. module_arch_cleanup() is called earlier under
> free_arch_cleanup.

Gah. Good catch. How about we add an additional check to see if
mod->state is MODULE_STATE_LIVE? If so, we can return. This means
we're coming from do_init_module(). If module_arch_freeing_init() was
called and the module was in a state other than MODULE_STATE_LIVE
(UNFORMED, GOING, COMING), we know we need to free. Think that would
work?

Jessica
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/