From: Dmitry Vyukov <dvyukov@google.com>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Alexander Potapenko <glider@google.com>,
Marco Elver <elver@google.com>,
Evgenii Stepanov <eugenis@google.com>,
Branislav Rankov <Branislav.Rankov@arm.com>,
Kevin Brodsky <kevin.brodsky@arm.com>,
kasan-dev <kasan-dev@googlegroups.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH mm v3 18/19] kasan, mm: allow cache merging with no metadata
Date: Tue, 17 Nov 2020 14:25:26 +0100 [thread overview]
Message-ID: <CACT4Y+azmp-xczEt5rQmejtrnQ=e9PFC15tOHTjA3nHfgQ5gpg@mail.gmail.com> (raw)
In-Reply-To: <6f0a1e72783ddac000ac08e7315b1d7c0ca4ec51.1605305978.git.andreyknvl@google.com>
On Fri, Nov 13, 2020 at 11:20 PM Andrey Konovalov <andreyknvl@google.com> wrote:
>
> The reason cache merging is disabled with KASAN is because KASAN puts its
> metadata right after the allocated object. When the merged caches have
> slightly different sizes, the metadata ends up in different places, which
> KASAN doesn't support.
>
> It might be possible to adjust the metadata allocation algorithm and make
> it friendly to the cache merging code. Instead this change takes a simpler
> approach and allows merging caches when no metadata is present. Which is
> the case for hardware tag-based KASAN with kasan.mode=prod.
>
> Co-developed-by: Vincenzo Frascino <Vincenzo.Frascino@arm.com>
> Signed-off-by: Vincenzo Frascino <Vincenzo.Frascino@arm.com>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> Link: https://linux-review.googlesource.com/id/Ia114847dfb2244f297d2cb82d592bf6a07455dba
Somehow gerrit contains an old version... so I was going to
independently propose what Marco already proposed as simplification...
until I looked at the patch in the email :)
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
> ---
> include/linux/kasan.h | 21 +++++++++++++++++++--
> mm/kasan/common.c | 11 +++++++++++
> mm/slab_common.c | 3 ++-
> 3 files changed, 32 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 16cf53eac29b..173a8e81d001 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -81,17 +81,30 @@ struct kasan_cache {
> };
>
> #ifdef CONFIG_KASAN_HW_TAGS
> +
> DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
> +
> static __always_inline bool kasan_enabled(void)
> {
> return static_branch_likely(&kasan_flag_enabled);
> }
> -#else
> +
> +#else /* CONFIG_KASAN_HW_TAGS */
> +
> static inline bool kasan_enabled(void)
> {
> return true;
> }
> -#endif
> +
> +#endif /* CONFIG_KASAN_HW_TAGS */
> +
> +slab_flags_t __kasan_never_merge(void);
> +static __always_inline slab_flags_t kasan_never_merge(void)
> +{
> + if (kasan_enabled())
> + return __kasan_never_merge();
> + return 0;
> +}
>
> void __kasan_unpoison_range(const void *addr, size_t size);
> static __always_inline void kasan_unpoison_range(const void *addr, size_t size)
> @@ -238,6 +251,10 @@ static inline bool kasan_enabled(void)
> {
> return false;
> }
> +static inline slab_flags_t kasan_never_merge(void)
> +{
> + return 0;
> +}
> static inline void kasan_unpoison_range(const void *address, size_t size) {}
> static inline void kasan_alloc_pages(struct page *page, unsigned int order) {}
> static inline void kasan_free_pages(struct page *page, unsigned int order) {}
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index cf874243efab..a5a4dcb1254d 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -87,6 +87,17 @@ asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
> }
> #endif /* CONFIG_KASAN_STACK */
>
> +/*
> + * Only allow cache merging when stack collection is disabled and no metadata
> + * is present.
> + */
> +slab_flags_t __kasan_never_merge(void)
> +{
> + if (kasan_stack_collection_enabled())
> + return SLAB_KASAN;
> + return 0;
> +}
> +
> void __kasan_alloc_pages(struct page *page, unsigned int order)
> {
> u8 tag;
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 0b5ae1819a8b..075b23ce94ec 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -19,6 +19,7 @@
> #include <linux/seq_file.h>
> #include <linux/proc_fs.h>
> #include <linux/debugfs.h>
> +#include <linux/kasan.h>
> #include <asm/cacheflush.h>
> #include <asm/tlbflush.h>
> #include <asm/page.h>
> @@ -54,7 +55,7 @@ static DECLARE_WORK(slab_caches_to_rcu_destroy_work,
> */
> #define SLAB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
> SLAB_TRACE | SLAB_TYPESAFE_BY_RCU | SLAB_NOLEAKTRACE | \
> - SLAB_FAILSLAB | SLAB_KASAN)
> + SLAB_FAILSLAB | kasan_never_merge())
>
> #define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT | SLAB_CACHE_DMA | \
> SLAB_CACHE_DMA32 | SLAB_ACCOUNT)
> --
> 2.29.2.299.gdc1121823c-goog
>
next prev parent reply other threads:[~2020-11-17 13:25 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-13 22:19 [PATCH mm v3 00/19] kasan: boot parameters for hardware tag-based mode Andrey Konovalov
2020-11-13 22:19 ` [PATCH mm v3 01/19] kasan: simplify quarantine_put call site Andrey Konovalov
2020-11-13 22:19 ` [PATCH mm v3 02/19] kasan: rename get_alloc/free_info Andrey Konovalov
2020-11-13 22:19 ` [PATCH mm v3 03/19] kasan: introduce set_alloc_info Andrey Konovalov
2020-11-13 22:19 ` [PATCH mm v3 04/19] kasan, arm64: unpoison stack only with CONFIG_KASAN_STACK Andrey Konovalov
2020-11-16 11:00 ` Dmitry Vyukov
2020-11-13 22:19 ` [PATCH mm v3 05/19] kasan: allow VMAP_STACK for HW_TAGS mode Andrey Konovalov
2020-11-16 11:01 ` Dmitry Vyukov
2020-11-13 22:19 ` [PATCH mm v3 06/19] kasan: remove __kasan_unpoison_stack Andrey Konovalov
2020-11-13 22:19 ` [PATCH mm v3 07/19] kasan: inline kasan_reset_tag for tag-based modes Andrey Konovalov
2020-11-17 10:56 ` Dmitry Vyukov
2020-11-13 22:19 ` [PATCH mm v3 08/19] kasan: inline random_tag for HW_TAGS Andrey Konovalov
2020-11-17 10:58 ` Dmitry Vyukov
2020-11-13 22:19 ` [PATCH mm v3 09/19] kasan: open-code kasan_unpoison_slab Andrey Konovalov
2020-11-16 15:06 ` Marco Elver
2020-11-13 22:20 ` [PATCH mm v3 10/19] kasan: inline (un)poison_range and check_invalid_free Andrey Konovalov
2020-11-16 15:11 ` Marco Elver
2020-11-13 22:20 ` [PATCH mm v3 11/19] kasan: add and integrate kasan boot parameters Andrey Konovalov
2020-11-16 15:15 ` Marco Elver
2020-11-17 11:09 ` Dmitry Vyukov
2020-11-13 22:20 ` [PATCH mm v3 12/19] kasan, mm: check kasan_enabled in annotations Andrey Konovalov
2020-11-16 15:26 ` Marco Elver
2020-11-17 11:12 ` Dmitry Vyukov
2020-11-13 22:20 ` [PATCH mm v3 13/19] kasan, mm: rename kasan_poison_kfree Andrey Konovalov
2020-11-16 15:43 ` Marco Elver
2020-11-13 22:20 ` [PATCH mm v3 14/19] kasan: don't round_up too much Andrey Konovalov
2020-11-13 22:20 ` [PATCH mm v3 15/19] kasan: simplify assign_tag and set_tag calls Andrey Konovalov
2020-11-13 22:20 ` [PATCH mm v3 16/19] kasan: clarify comment in __kasan_kfree_large Andrey Konovalov
2020-11-13 22:20 ` [PATCH mm v3 17/19] kasan: clean up metadata allocation and usage Andrey Konovalov
2020-11-16 15:46 ` Marco Elver
2020-11-17 13:12 ` Dmitry Vyukov
2020-11-17 13:18 ` Marco Elver
2020-11-17 13:27 ` Dmitry Vyukov
2020-11-23 18:54 ` Andrey Konovalov
2020-11-23 19:16 ` Andrey Konovalov
2020-11-13 22:20 ` [PATCH mm v3 18/19] kasan, mm: allow cache merging with no metadata Andrey Konovalov
2020-11-16 15:45 ` Marco Elver
2020-11-17 13:25 ` Dmitry Vyukov [this message]
2020-11-23 13:52 ` Andrey Konovalov
2020-11-13 22:20 ` [PATCH mm v3 19/19] kasan: update documentation Andrey Konovalov
2020-11-16 15:47 ` Marco Elver
2020-11-17 13:28 ` Dmitry Vyukov
2020-11-16 14:48 ` [PATCH mm v3 00/19] kasan: boot parameters for hardware tag-based mode Vincenzo Frascino
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