On Wed, Apr 15, 2020 at 05:02:16PM +0200, Jessica Yu wrote:
> +++ Josh Poimboeuf [14/04/20 11:28 -0500]:
> > With arch_klp_init_object_loaded() gone, and apply_relocate_add() now
> > using text_poke(), livepatch no longer needs to use module_disable_ro().
> >
> > The text_mutex usage can also be removed -- its purpose was to protect
> > against module permission change races.
> >
> > Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> > ---
> > kernel/livepatch/core.c | 8 --------
> > 1 file changed, 8 deletions(-)
> >
> > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> > index 817676caddee..3a88639b3326 100644
> > --- a/kernel/livepatch/core.c
> > +++ b/kernel/livepatch/core.c
> > @@ -767,10 +767,6 @@ static int klp_init_object_loaded(struct klp_patch *patch,
> > struct klp_modinfo *info = patch->mod->klp_info;
> >
> > if (klp_is_module(obj)) {
> > -
> > - mutex_lock(&text_mutex);
> > - module_disable_ro(patch->mod);
> > -
>
> Don't you still need the text_mutex to use text_poke() though?
> (Through klp_write_relocations -> apply_relocate_add -> text_poke)
> At least, I see this assertion there:
>
> void *text_poke(void *addr, const void *opcode, size_t len)
> {
> lockdep_assert_held(&text_mutex);
>
> return __text_poke(addr, opcode, len);
> }
Hm, guess I should have tested with lockdep ;-)
--
Josh
