| Message ID | 20210705103229.8505-3-yee.lee@mediatek.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v6,1/2] mm: move helper to check slub_debug_enabled | expand |
On Mon, 5 Jul 2021 at 12:33, <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. > > The penalty is acceptable since they are only enabled in debug mode, > not production builds. A block of comment is added for explanation. > > Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> > Cc: Alexander Potapenko <glider@google.com> > Cc: Dmitry Vyukov <dvyukov@google.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Suggested-by: Marco Elver <elver@google.com> > Suggested-by: Andrey Konovalov <andreyknvl@gmail.com> > Signed-off-by: Yee Lee <yee.lee@mediatek.com> Reviewed-by: Marco Elver <elver@google.com> Thank you! > --- > mm/kasan/kasan.h | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 98e3059bfea4..d739cdd1621a 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -9,6 +9,7 @@ > #ifdef CONFIG_KASAN_HW_TAGS > > #include <linux/static_key.h> > +#include "../slab.h" > > DECLARE_STATIC_KEY_FALSE(kasan_flag_stacktrace); > extern bool kasan_flag_async __ro_after_init; > @@ -387,6 +388,17 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init) > > if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) > return; > + /* > + * 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. > + */ > + if (__slub_debug_enabled() && > + init && ((unsigned long)size & KASAN_GRANULE_MASK)) { > + init = false; > + memzero_explicit((void *)addr, size); > + } > size = round_up(size, KASAN_GRANULE_SIZE); > > hw_set_mem_tag_range((void *)addr, size, tag, init); > -- > 2.18.0
On Mon, Jul 5, 2021 at 12:33 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. > > The penalty is acceptable since they are only enabled in debug mode, > not production builds. A block of comment is added for explanation. > > Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> > Cc: Alexander Potapenko <glider@google.com> > Cc: Dmitry Vyukov <dvyukov@google.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Suggested-by: Marco Elver <elver@google.com> > Suggested-by: Andrey Konovalov <andreyknvl@gmail.com> > Signed-off-by: Yee Lee <yee.lee@mediatek.com> > --- > mm/kasan/kasan.h | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 98e3059bfea4..d739cdd1621a 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -9,6 +9,7 @@ > #ifdef CONFIG_KASAN_HW_TAGS > > #include <linux/static_key.h> > +#include "../slab.h" > > DECLARE_STATIC_KEY_FALSE(kasan_flag_stacktrace); > extern bool kasan_flag_async __ro_after_init; > @@ -387,6 +388,17 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init) > > if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) > return; > + /* > + * 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. > + */ > + if (__slub_debug_enabled() && What happened to slub_debug_enabled_unlikely()? Was it renamed? Why? I didn't receive patch #1 of v6 (nor of v5). > + init && ((unsigned long)size & KASAN_GRANULE_MASK)) { > + init = false; > + memzero_explicit((void *)addr, size); > + } > size = round_up(size, KASAN_GRANULE_SIZE); > > hw_set_mem_tag_range((void *)addr, size, tag, init); > -- > 2.18.0 >
On Mon, 5 Jul 2021 at 13:12, Andrey Konovalov <andreyknvl@gmail.com> wrote: [...] > > + /* > > + * 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. > > + */ > > + if (__slub_debug_enabled() && > > What happened to slub_debug_enabled_unlikely()? Was it renamed? Why? I > didn't receive patch #1 of v6 (nor of v5). Somebody had the same idea with the helper: https://lkml.kernel.org/r/YOKsC75kJfCZwySD@elver.google.com and Matthew didn't like the _unlikely() prefix. Which meant we should just move the existing helper introduced in the merge window. Patch 1/2: https://lkml.kernel.org/r/20210705103229.8505-2-yee.lee@mediatek.com Thanks, -- Marco
On Mon, Jul 5, 2021 at 1:18 PM Marco Elver <elver@google.com> wrote: > > On Mon, 5 Jul 2021 at 13:12, Andrey Konovalov <andreyknvl@gmail.com> wrote: > [...] > > > + /* > > > + * 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. > > > + */ > > > + if (__slub_debug_enabled() && > > > > What happened to slub_debug_enabled_unlikely()? Was it renamed? Why? I > > didn't receive patch #1 of v6 (nor of v5). > > Somebody had the same idea with the helper: > https://lkml.kernel.org/r/YOKsC75kJfCZwySD@elver.google.com > and Matthew didn't like the _unlikely() prefix. > > Which meant we should just move the existing helper introduced in the > merge window. > > Patch 1/2: https://lkml.kernel.org/r/20210705103229.8505-2-yee.lee@mediatek.com Got it. Thank you, Marco!
On Mon, Jul 5, 2021 at 12:33 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. > > The penalty is acceptable since they are only enabled in debug mode, > not production builds. A block of comment is added for explanation. > > Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> > Cc: Alexander Potapenko <glider@google.com> > Cc: Dmitry Vyukov <dvyukov@google.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Suggested-by: Marco Elver <elver@google.com> > Suggested-by: Andrey Konovalov <andreyknvl@gmail.com> > Signed-off-by: Yee Lee <yee.lee@mediatek.com> > --- > mm/kasan/kasan.h | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 98e3059bfea4..d739cdd1621a 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -9,6 +9,7 @@ > #ifdef CONFIG_KASAN_HW_TAGS > > #include <linux/static_key.h> > +#include "../slab.h" > > DECLARE_STATIC_KEY_FALSE(kasan_flag_stacktrace); > extern bool kasan_flag_async __ro_after_init; > @@ -387,6 +388,17 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init) > > if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) > return; > + /* > + * 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. > + */ > + if (__slub_debug_enabled() && > + init && ((unsigned long)size & KASAN_GRANULE_MASK)) { > + init = false; > + memzero_explicit((void *)addr, size); > + } > size = round_up(size, KASAN_GRANULE_SIZE); > > hw_set_mem_tag_range((void *)addr, size, tag, init); > -- > 2.18.0 > Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Thank you, Macro. I thought members in "suggested-by" would be put in the list as well... And thank you guys for the review these days. @Andrew Motom Hi Andrew, Could you help to push the patches? We are dealing with the issue and would backport to Android porject right after the action. Appreciated! BR, Yee On Mon, 2021-07-05 at 13:23 +0200, Andrey Konovalov wrote: > On Mon, Jul 5, 2021 at 1:18 PM Marco Elver <elver@google.com> wrote: > > > > On Mon, 5 Jul 2021 at 13:12, Andrey Konovalov <andreyknvl@gmail.com > > > wrote: > > [...] > > > > + /* > > > > + * 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. > > > > + */ > > > > + if (__slub_debug_enabled() && > > > > > > What happened to slub_debug_enabled_unlikely()? Was it renamed? > > > Why? I > > > didn't receive patch #1 of v6 (nor of v5). > > > > Somebody had the same idea with the helper: > > https://lkml.kernel.org/r/YOKsC75kJfCZwySD@elver.google.com > > and Matthew didn't like the _unlikely() prefix. > > > > Which meant we should just move the existing helper introduced in > > the > > merge window. > > > > Patch 1/2: > > https://lkml.kernel.org/r/20210705103229.8505-2-yee.lee@mediatek.com > > Got it. Thank you, Marco!
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 98e3059bfea4..d739cdd1621a 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -9,6 +9,7 @@ #ifdef CONFIG_KASAN_HW_TAGS #include <linux/static_key.h> +#include "../slab.h" DECLARE_STATIC_KEY_FALSE(kasan_flag_stacktrace); extern bool kasan_flag_async __ro_after_init; @@ -387,6 +388,17 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init) if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) return; + /* + * 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. + */ + if (__slub_debug_enabled() && + init && ((unsigned long)size & KASAN_GRANULE_MASK)) { + init = false; + memzero_explicit((void *)addr, size); + } size = round_up(size, KASAN_GRANULE_SIZE); hw_set_mem_tag_range((void *)addr, size, tag, init);