On Wed, 9 Dec 2020 at 19:57, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > On Wed, Dec 09, 2020 at 07:49:36PM +0100, Marco Elver wrote: > > On Wed, 9 Dec 2020 at 19:24, Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > > __ro_after_init static keys are incompatible with usage in loadable kernel > > > modules and cause crashes. Don't use those, use normal static keys. > > > > > > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > > > > Reviewed-by: Marco Elver <elver@xxxxxxxxxx> > > > > > --- > > > > > > This fix can be squashed into > > > "kasan: add and integrate kasan boot parameters". > > > > > > --- > > > mm/kasan/hw_tags.c | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c > > > index c91f2c06ecb5..55bd6f09c70f 100644 > > > --- a/mm/kasan/hw_tags.c > > > +++ b/mm/kasan/hw_tags.c > > > @@ -43,11 +43,11 @@ static enum kasan_arg_stacktrace kasan_arg_stacktrace __ro_after_init; > > > static enum kasan_arg_fault kasan_arg_fault __ro_after_init; > > > > > > /* Whether KASAN is enabled at all. */ > > > -DEFINE_STATIC_KEY_FALSE_RO(kasan_flag_enabled); > > > +DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled); > > > > Side-node: This appears to be just a bad interface; I think the macro > > DEFINE_STATIC_KEY_FALSE_RO() is error-prone, if it can't be guaranteed > > that this is always safe, since the presence of the macro encourages > > its use and we'll inevitably run into this problem again. > > > > > EXPORT_SYMBOL(kasan_flag_enabled); > > > > DEFINE_STATIC_KEY_FALSE_RO() + EXPORT_SYMBOL() is an immediate bug. > > Given its use has not increased substantially since its introduction, > > it may be safer to consider its removal. > > Right -- it seems the export is the problem, not the RO-ness. What is > actually trying to change the flag after __init? It seems to want to add it to a list on module loads: https://lore.kernel.org/lkml/20201208125129.GY2414@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ -- Marco
