| Message ID | 20210624112624.31215-2-yee.lee@mediatek.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,1/1] kasan: Add memzero init for unaligned size under SLUB debug | expand |
On Thu, Jun 24, 2021 at 2:26 PM <yee.lee@mediatek.com> wrote: > > From: Yee Lee <yee.lee@mediatek.com> > > Issue: when SLUB debug is on, hwtag kasan_unpoison() would overwrite > the redzone of object with unaligned size. > > An additional memzero_explicit() path is added to replacing init by > hwtag instruction for those unaligned size at SLUB debug mode. > > Signed-off-by: Yee Lee <yee.lee@mediatek.com> > --- > mm/kasan/kasan.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 8f450bc28045..d1054f35838f 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -387,6 +387,12 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init) > > if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) > return; > +#if IS_ENABLED(CONFIG_SLUB_DEBUG) Is this an issue only with SLUB? SLAB also uses redzones. > + if (init && ((unsigned long)size & KASAN_GRANULE_MASK)) { This needs a comment along the lines of: /* Explicitly initialize the memory with the precise object size to avoid overwriting the SLAB redzone. This disables initialization in the arch code and may thus lead to performance penalty. The penalty is accepted since SLAB redzones aren't enabled in production builds. */ > + init = false; > + memzero_explicit((void *)addr, size); > + } > +#endif > size = round_up(size, KASAN_GRANULE_SIZE); > > hw_set_mem_tag_range((void *)addr, size, tag, init); > -- > 2.18.0 >
On Fri, 2021-06-25 at 17:03 +0300, Andrey Konovalov wrote: > On Thu, Jun 24, 2021 at 2:26 PM <yee.lee@mediatek.com> wrote: > > > > From: Yee Lee <yee.lee@mediatek.com> > > > > Issue: when SLUB debug is on, hwtag kasan_unpoison() would > > overwrite > > the redzone of object with unaligned size. > > > > An additional memzero_explicit() path is added to replacing init by > > hwtag instruction for those unaligned size at SLUB debug mode. > > > > Signed-off-by: Yee Lee <yee.lee@mediatek.com> > > --- > > mm/kasan/kasan.h | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > > index 8f450bc28045..d1054f35838f 100644 > > --- a/mm/kasan/kasan.h > > +++ b/mm/kasan/kasan.h > > @@ -387,6 +387,12 @@ static inline void kasan_unpoison(const void > > *addr, size_t size, bool init) > > > > if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) > > return; > > +#if IS_ENABLED(CONFIG_SLUB_DEBUG) > > Is this an issue only with SLUB? SLAB also uses redzones. As I known, hw-tag kasan only works with SLUB. > > > + if (init && ((unsigned long)size & KASAN_GRANULE_MASK)) { > > This needs a comment along the lines of: > > /* Explicitly initialize the memory with the precise object size to > avoid overwriting the SLAB redzone. This disables initialization in > the arch code and may thus lead to performance penalty. The penalty > is > accepted since SLAB redzones aren't enabled in production builds. */ Sure, will work on this. > > > + init = false; > > + memzero_explicit((void *)addr, size); > > + } > > +#endif > > size = round_up(size, KASAN_GRANULE_SIZE); > > > > hw_set_mem_tag_range((void *)addr, size, tag, init); > > -- > > 2.18.0 > >
On Thu, 24 Jun 2021 at 13:27, <yee.lee@mediatek.com> wrote: > > From: Yee Lee <yee.lee@mediatek.com> > > Issue: when SLUB debug is on, hwtag kasan_unpoison() would overwrite > the redzone of object with unaligned size. > > An additional memzero_explicit() path is added to replacing init by > hwtag instruction for those unaligned size at SLUB debug mode. > > Signed-off-by: Yee Lee <yee.lee@mediatek.com> > --- > mm/kasan/kasan.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 8f450bc28045..d1054f35838f 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -387,6 +387,12 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init) > > if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) > return; > +#if IS_ENABLED(CONFIG_SLUB_DEBUG) Avoid the #if. I think none of the stuff referenced here is only available if CONFIG_SLUB_DEBUG. In that case, please just write: if (IS_ENABLED(CONFIG_SLUB_DEBUG) && init && .........) { The compiler will correctly optimize out the branch if the config option is not enabled. But the benefit is we compile-test this code with all configs. > + if (init && ((unsigned long)size & KASAN_GRANULE_MASK)) { > + init = false; > + memzero_explicit((void *)addr, size); > + } > +#endif Thanks, -- Marco
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 8f450bc28045..d1054f35838f 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -387,6 +387,12 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init) if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) return; +#if IS_ENABLED(CONFIG_SLUB_DEBUG) + if (init && ((unsigned long)size & KASAN_GRANULE_MASK)) { + init = false; + memzero_explicit((void *)addr, size); + } +#endif size = round_up(size, KASAN_GRANULE_SIZE); hw_set_mem_tag_range((void *)addr, size, tag, init);