| Message ID | 20210319144058.772525-3-dja@axtens.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KASAN for powerpc64 radix | expand |
On Fri, 19 Mar 2021 at 15:41, Daniel Axtens <dja@axtens.net> wrote: > Allow architectures to define a kasan_arch_is_ready() hook that bails > out of any function that's about to touch the shadow unless the arch > says that it is ready for the memory to be accessed. This is fairly > uninvasive and should have a negligible performance penalty. > > This will only work in outline mode, so an arch must specify > ARCH_DISABLE_KASAN_INLINE if it requires this. > > Cc: Balbir Singh <bsingharora@gmail.com> > Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> > Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu> > Signed-off-by: Daniel Axtens <dja@axtens.net> > > -- > > I discuss the justfication for this later in the series. Also, > both previous RFCs for ppc64 - by 2 different people - have > needed this trick! See: > - https://lore.kernel.org/patchwork/patch/592820/ # ppc64 hash series > - https://patchwork.ozlabs.org/patch/795211/ # ppc radix series > --- > include/linux/kasan.h | 4 ++++ > mm/kasan/common.c | 4 ++++ > mm/kasan/generic.c | 3 +++ > mm/kasan/shadow.c | 4 ++++ > 4 files changed, 15 insertions(+) > > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > index 8b3b99d659b7..6bd8343f0033 100644 > --- a/include/linux/kasan.h > +++ b/include/linux/kasan.h Does kasan_arch_is_ready() need to be defined in the public interface of KASAN? Could it instead be moved to mm/kasan/kasan.h? > @@ -23,6 +23,10 @@ struct kunit_kasan_expectation { > > #endif > > +#ifndef kasan_arch_is_ready > +static inline bool kasan_arch_is_ready(void) { return true; } > +#endif > + > #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) > > #include <linux/pgtable.h> > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index 6bb87f2acd4e..f23a9e2dce9f 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -345,6 +345,10 @@ static inline bool ____kasan_slab_free(struct kmem_cache *cache, void *object, > if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU)) > return false; > > + /* We can't read the shadow byte if the arch isn't ready */ > + if (!kasan_arch_is_ready()) > + return false; > + While it probably doesn't matter much, it seems this check could be moved up, rather than having it in the middle here. > if (!kasan_byte_accessible(tagged_object)) { > kasan_report_invalid_free(tagged_object, ip); > return true; > diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c > index 53cbf28859b5..c3f5ba7a294a 100644 > --- a/mm/kasan/generic.c > +++ b/mm/kasan/generic.c > @@ -163,6 +163,9 @@ static __always_inline bool check_region_inline(unsigned long addr, > size_t size, bool write, > unsigned long ret_ip) > { > + if (!kasan_arch_is_ready()) > + return true; > + > if (unlikely(size == 0)) > return true; > > diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c > index 727ad4629173..1f650c521037 100644 > --- a/mm/kasan/shadow.c > +++ b/mm/kasan/shadow.c > @@ -80,6 +80,10 @@ void kasan_poison(const void *addr, size_t size, u8 value, bool init) > */ > addr = kasan_reset_tag(addr); > > + /* Don't touch the shadow memory if arch isn't ready */ > + if (!kasan_arch_is_ready()) > + return; > + > /* Skip KFENCE memory if called explicitly outside of sl*b. */ > if (is_kfence_address(addr)) > return; > -- > 2.27.0 > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20210319144058.772525-3-dja%40axtens.net.
diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 8b3b99d659b7..6bd8343f0033 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -23,6 +23,10 @@ struct kunit_kasan_expectation { #endif +#ifndef kasan_arch_is_ready +static inline bool kasan_arch_is_ready(void) { return true; } +#endif + #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) #include <linux/pgtable.h> diff --git a/mm/kasan/common.c b/mm/kasan/common.c index 6bb87f2acd4e..f23a9e2dce9f 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -345,6 +345,10 @@ static inline bool ____kasan_slab_free(struct kmem_cache *cache, void *object, if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU)) return false; + /* We can't read the shadow byte if the arch isn't ready */ + if (!kasan_arch_is_ready()) + return false; + if (!kasan_byte_accessible(tagged_object)) { kasan_report_invalid_free(tagged_object, ip); return true; diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c index 53cbf28859b5..c3f5ba7a294a 100644 --- a/mm/kasan/generic.c +++ b/mm/kasan/generic.c @@ -163,6 +163,9 @@ static __always_inline bool check_region_inline(unsigned long addr, size_t size, bool write, unsigned long ret_ip) { + if (!kasan_arch_is_ready()) + return true; + if (unlikely(size == 0)) return true; diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c index 727ad4629173..1f650c521037 100644 --- a/mm/kasan/shadow.c +++ b/mm/kasan/shadow.c @@ -80,6 +80,10 @@ void kasan_poison(const void *addr, size_t size, u8 value, bool init) */ addr = kasan_reset_tag(addr); + /* Don't touch the shadow memory if arch isn't ready */ + if (!kasan_arch_is_ready()) + return; + /* Skip KFENCE memory if called explicitly outside of sl*b. */ if (is_kfence_address(addr)) return;
Allow architectures to define a kasan_arch_is_ready() hook that bails out of any function that's about to touch the shadow unless the arch says that it is ready for the memory to be accessed. This is fairly uninvasive and should have a negligible performance penalty. This will only work in outline mode, so an arch must specify ARCH_DISABLE_KASAN_INLINE if it requires this. Cc: Balbir Singh <bsingharora@gmail.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Daniel Axtens <dja@axtens.net> -- I discuss the justfication for this later in the series. Also, both previous RFCs for ppc64 - by 2 different people - have needed this trick! See: - https://lore.kernel.org/patchwork/patch/592820/ # ppc64 hash series - https://patchwork.ozlabs.org/patch/795211/ # ppc radix series --- include/linux/kasan.h | 4 ++++ mm/kasan/common.c | 4 ++++ mm/kasan/generic.c | 3 +++ mm/kasan/shadow.c | 4 ++++ 4 files changed, 15 insertions(+)