Messages in this thread | | | From | Andrey Konovalov <> | Date | Fri, 16 Oct 2020 15:10:43 +0200 | Subject | Re: [PATCH RFC 8/8] kasan: add and integrate kasan_mode boot param |
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On Thu, Oct 15, 2020 at 3:56 PM Marco Elver <elver@google.com> wrote: > > On Wed, 14 Oct 2020 at 22:45, Andrey Konovalov <andreyknvl@google.com> wrote: > >
[...]
> > @@ -180,6 +182,7 @@ size_t kasan_metadata_size(struct kmem_cache *cache) > > struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache, > > const void *object) > > { > > + WARN_ON(!static_branch_unlikely(&kasan_debug)); > > The WARN_ON condition itself should be unlikely, so that would imply > that the static branch here should be likely since you're negating it.
Here I was thinking that we should optimize for the production use case, which shouldn't have kasan_debug enabled, hence the unlikely. But technically this function shouldn't be called in production anyway, so likely will do fine too.
> And AFAIK, this function should only be called if kasan_debug is true.
Yes, this WARN_ON is to make sure this doesn't happen.
[...]
> > +/* Whether to use syncronous or asynchronous tag checking. */ > > +static bool kasan_sync __ro_after_init; > > s/syncronous/synchronous/
Ack.
> > > +static int __init early_kasan_mode(char *arg) > > +{ > > + if (!arg) > > + return -EINVAL; > > + > > + if (strcmp(arg, "on") == 0) > > + kasan_mode = KASAN_MODE_ON; > > + else if (strcmp(arg, "debug") == 0) > > s/strcmp(..) == 0/!strcmp(..)/ ?
Sounds good.
[...]
> > @@ -60,6 +111,7 @@ void kasan_set_free_info(struct kmem_cache *cache, > > { > > struct kasan_alloc_meta *alloc_meta; > > > > + WARN_ON(!static_branch_unlikely(&kasan_debug)); > > What actually happens if any of these are called with !kasan_debug and > the warning triggers? Is it still valid to execute the below, or > should it bail out? Or possibly even disable KASAN entirely?
It shouldn't happen, but if it happens maybe it indeed makes sense to disable KASAN here is a failsafe. It might be tricky to disable MTE though, but I'll see what we can do here.
Thank you!
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