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Date: Mon, 20 Jun 2022 15:39:42 +0200
From: Marco Elver <elver@...gle.com>
To: andrey.konovalov@...ux.dev
Cc: Alexander Potapenko <glider@...gle.com>,
Andrey Konovalov <andreyknvl@...il.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Andrey Ryabinin <ryabinin.a.a@...il.com>,
kasan-dev@...glegroups.com, Peter Collingbourne <pcc@...gle.com>,
Evgenii Stepanov <eugenis@...gle.com>,
Florian Mayer <fmayer@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH 05/32] kasan: drop CONFIG_KASAN_TAGS_IDENTIFY
On Mon, 13 Jun 2022 at 22:15, <andrey.konovalov@...ux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@...gle.com>
>
> Drop CONFIG_KASAN_TAGS_IDENTIFY and related code to simplify making
> changes to the reporting code.
>
> The dropped functionality will be restored in the following patches in
> this series.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
Reviewed-by: Marco Elver <elver@...gle.com>
> ---
> lib/Kconfig.kasan | 8 --------
> mm/kasan/kasan.h | 12 +-----------
> mm/kasan/report_tags.c | 28 ----------------------------
> mm/kasan/tags.c | 21 ++-------------------
> 4 files changed, 3 insertions(+), 66 deletions(-)
>
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index f0973da583e0..ca09b1cf8ee9 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -167,14 +167,6 @@ config KASAN_STACK
> as well, as it adds inline-style instrumentation that is run
> unconditionally.
>
> -config KASAN_TAGS_IDENTIFY
> - bool "Memory corruption type identification"
> - depends on KASAN_SW_TAGS || KASAN_HW_TAGS
> - help
> - Enables best-effort identification of the bug types (use-after-free
> - or out-of-bounds) at the cost of increased memory consumption.
> - Only applicable for the tag-based KASAN modes.
> -
> config KASAN_VMALLOC
> bool "Check accesses to vmalloc allocations"
> depends on HAVE_ARCH_KASAN_VMALLOC
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 610057e651d2..aa6b43936f8d 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -168,23 +168,13 @@ struct kasan_track {
> depot_stack_handle_t stack;
> };
>
> -#if defined(CONFIG_KASAN_TAGS_IDENTIFY) && defined(CONFIG_KASAN_SW_TAGS)
> -#define KASAN_NR_FREE_STACKS 5
> -#else
> -#define KASAN_NR_FREE_STACKS 1
> -#endif
> -
> struct kasan_alloc_meta {
> struct kasan_track alloc_track;
> /* Generic mode stores free track in kasan_free_meta. */
> #ifdef CONFIG_KASAN_GENERIC
> depot_stack_handle_t aux_stack[2];
> #else
> - struct kasan_track free_track[KASAN_NR_FREE_STACKS];
> -#endif
> -#ifdef CONFIG_KASAN_TAGS_IDENTIFY
> - u8 free_pointer_tag[KASAN_NR_FREE_STACKS];
> - u8 free_track_idx;
> + struct kasan_track free_track;
> #endif
> };
>
> diff --git a/mm/kasan/report_tags.c b/mm/kasan/report_tags.c
> index e25d2166e813..35cf3cae4aa4 100644
> --- a/mm/kasan/report_tags.c
> +++ b/mm/kasan/report_tags.c
> @@ -5,37 +5,9 @@
> */
>
> #include "kasan.h"
> -#include "../slab.h"
>
> const char *kasan_get_bug_type(struct kasan_report_info *info)
> {
> -#ifdef CONFIG_KASAN_TAGS_IDENTIFY
> - struct kasan_alloc_meta *alloc_meta;
> - struct kmem_cache *cache;
> - struct slab *slab;
> - const void *addr;
> - void *object;
> - u8 tag;
> - int i;
> -
> - tag = get_tag(info->access_addr);
> - addr = kasan_reset_tag(info->access_addr);
> - slab = kasan_addr_to_slab(addr);
> - if (slab) {
> - cache = slab->slab_cache;
> - object = nearest_obj(cache, slab, (void *)addr);
> - alloc_meta = kasan_get_alloc_meta(cache, object);
> -
> - if (alloc_meta) {
> - for (i = 0; i < KASAN_NR_FREE_STACKS; i++) {
> - if (alloc_meta->free_pointer_tag[i] == tag)
> - return "use-after-free";
> - }
> - }
> - return "out-of-bounds";
> - }
> -#endif
> -
> /*
> * If access_size is a negative number, then it has reason to be
> * defined as out-of-bounds bug type.
> diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
> index 1ba3c8399f72..e0e5de8ce834 100644
> --- a/mm/kasan/tags.c
> +++ b/mm/kasan/tags.c
> @@ -30,39 +30,22 @@ void kasan_save_free_info(struct kmem_cache *cache,
> void *object, u8 tag)
> {
> struct kasan_alloc_meta *alloc_meta;
> - u8 idx = 0;
>
> alloc_meta = kasan_get_alloc_meta(cache, object);
> if (!alloc_meta)
> return;
>
> -#ifdef CONFIG_KASAN_TAGS_IDENTIFY
> - idx = alloc_meta->free_track_idx;
> - alloc_meta->free_pointer_tag[idx] = tag;
> - alloc_meta->free_track_idx = (idx + 1) % KASAN_NR_FREE_STACKS;
> -#endif
> -
> - kasan_set_track(&alloc_meta->free_track[idx], GFP_NOWAIT);
> + kasan_set_track(&alloc_meta->free_track, GFP_NOWAIT);
> }
>
> struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
> void *object, u8 tag)
> {
> struct kasan_alloc_meta *alloc_meta;
> - int i = 0;
>
> alloc_meta = kasan_get_alloc_meta(cache, object);
> if (!alloc_meta)
> return NULL;
>
> -#ifdef CONFIG_KASAN_TAGS_IDENTIFY
> - for (i = 0; i < KASAN_NR_FREE_STACKS; i++) {
> - if (alloc_meta->free_pointer_tag[i] == tag)
> - break;
> - }
> - if (i == KASAN_NR_FREE_STACKS)
> - i = alloc_meta->free_track_idx;
> -#endif
> -
> - return &alloc_meta->free_track[i];
> + return &alloc_meta->free_track;
> }
> --
> 2.25.1
>
> --
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