Re: [PATCH v2 00/11] kasan: unify kasan_arch_is_ready with kasan_enabled

[Sabyrzhan Tasbolatov <snovitoll@gmail.com>]

On Sat, Jun 28, 2025 at 3:57 PM Andrey Konovalov <andreyknvl@gmail.com> wrote:
>
> On Thu, Jun 26, 2025 at 5:32 PM Sabyrzhan Tasbolatov
> <snovitoll@gmail.com> wrote:
> >
> > This patch series unifies the kasan_arch_is_ready() and kasan_enabled()
> > interfaces by extending the existing kasan_enabled() infrastructure to
> > work consistently across all KASAN modes (Generic, SW_TAGS, HW_TAGS).
> >
> > Currently, kasan_enabled() only works for HW_TAGS mode using a static key,
> > while other modes either return IS_ENABLED(CONFIG_KASAN) (compile-time
> > constant) or rely on architecture-specific kasan_arch_is_ready()
> > implementations with custom static keys and global variables.
> >
> > This leads to:
> > - Code duplication across architectures
> > - Inconsistent runtime behavior between KASAN modes
> > - Architecture-specific readiness tracking
> >
> > After this series:
> > - All KASAN modes use the same kasan_flag_enabled static key
> > - Consistent runtime enable/disable behavior across modes
> > - Simplified architecture code with unified kasan_init_generic() calls
> > - Elimination of arch specific kasan_arch_is_ready() implementations
> > - Unified vmalloc integration using kasan_enabled() checks
> >
> > This addresses the bugzilla issue [1] about making
> > kasan_flag_enabled and kasan_enabled() work for Generic mode,
> > and extends it to provide true unification across all modes.
> >
> > [1] https://bugzilla.kernel.org/show_bug.cgi?id=217049
>
> Hi Sabyrzhan,
>
> Thank you for working on this!
>
> One aspect that is missing from the patches is moving the
> kasan_arch_is_ready() calls into the include/linux/kasan.h (this is
> not explicitly mentioned in the issue, but this is what the "adding
> __wrappers" part is about).
>
> Another thing that needs careful consideration is whether it's
> possible to combine kasan_arch_is_ready() and kasan_enabled() into the
> same check logically at all. There's one issue mentioned in [1]:

Hello,
I've removed kasan_arch_is_ready() at all in this series:
[PATCH v2 11/11] kasan: replace kasan_arch_is_ready with kasan_enabled

Is it not what's expected by unification?

>
> > In kasan_cache_create() we unconditionally allocate a metadata buffer,
> > but the kasan_init_slab_obj() call to initialise it is guarded by
> > kasan_enabled(). But later parts of the code only check the presence of
> > the buffer before using it, so bad things happen if kasan_enabled()
> > later turns on (I was getting some error about invalid lock state).
>
> And there might be other callbacks that should be executed even before
> kasan_init_...() completes. But then for the HW_TAGS mode, if
> kasan_enabled() is off, then we don't want to execute any callbacks.
>
> So maybe we do actually need a separate static key for
> kasan_arch_is_ready(). But even if so, it still makes sense to move
> kasan_arch_is_ready() into the __wrappers for the affected callbacks.
>
> Thanks!
>
> [1] https://lore.kernel.org/linux-mm/CA+fCnZf7JqTH46C7oG2Wk9NnLU7hgiVDEK0EA8RAtyr-KgkHdg@mail.gmail.com/