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Date: Wed, 11 Nov 2020 16:22:05 +0100
From: Alexander Potapenko <glider@...gle.com>
To: Andrey Konovalov <andreyknvl@...gle.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Marco Elver <elver@...gle.com>,
Evgenii Stepanov <eugenis@...gle.com>,
Branislav Rankov <Branislav.Rankov@....com>,
Kevin Brodsky <kevin.brodsky@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
kasan-dev <kasan-dev@...glegroups.com>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Memory Management List <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 23/44] kasan: separate metadata_fetch_row for each mode
On Tue, Nov 10, 2020 at 11:12 PM Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> This is a preparatory commit for the upcoming addition of a new hardware
> tag-based (MTE-based) KASAN mode.
>
> Rework print_memory_metadata() to make it agnostic with regard to the
> way metadata is stored. Allow providing a separate metadata_fetch_row()
> implementation for each KASAN mode. Hardware tag-based KASAN will provide
> its own implementation that doesn't use shadow memory.
>
> No functional changes for software modes.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....com>
> Reviewed-by: Marco Elver <elver@...gle.com>
> ---
> Change-Id: I5b0ed1d079ea776e620beca6a529a861e7dced95
> ---
> mm/kasan/kasan.h | 8 ++++++
> mm/kasan/report.c | 56 +++++++++++++++++++--------------------
> mm/kasan/report_generic.c | 5 ++++
> mm/kasan/report_sw_tags.c | 5 ++++
> 4 files changed, 45 insertions(+), 29 deletions(-)
>
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index f9366dfd94c9..b5b00bff358f 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -57,6 +57,13 @@
> #define KASAN_ABI_VERSION 1
> #endif
>
> +/* Metadata layout customization. */
> +#define META_BYTES_PER_BLOCK 1
> +#define META_BLOCKS_PER_ROW 16
> +#define META_BYTES_PER_ROW (META_BLOCKS_PER_ROW * META_BYTES_PER_BLOCK)
> +#define META_MEM_BYTES_PER_ROW (META_BYTES_PER_ROW * KASAN_GRANULE_SIZE)
> +#define META_ROWS_AROUND_ADDR 2
> +
> struct kasan_access_info {
> const void *access_addr;
> const void *first_bad_addr;
> @@ -168,6 +175,7 @@ bool check_invalid_free(void *addr);
>
> void *find_first_bad_addr(void *addr, size_t size);
> const char *get_bug_type(struct kasan_access_info *info);
> +void metadata_fetch_row(char *buffer, void *row);
>
> #if defined(CONFIG_KASAN_GENERIC) && CONFIG_KASAN_STACK
> void print_address_stack_frame(const void *addr);
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 8c588588c88f..8afc1a6ab202 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -33,12 +33,6 @@
> #include "kasan.h"
> #include "../slab.h"
>
> -/* Metadata layout customization. */
> -#define META_BYTES_PER_BLOCK 1
> -#define META_BLOCKS_PER_ROW 16
> -#define META_BYTES_PER_ROW (META_BLOCKS_PER_ROW * META_BYTES_PER_BLOCK)
> -#define META_ROWS_AROUND_ADDR 2
> -
> static unsigned long kasan_flags;
>
> #define KASAN_BIT_REPORTED 0
> @@ -238,55 +232,59 @@ static void print_address_description(void *addr, u8 tag)
> print_address_stack_frame(addr);
> }
>
> -static bool row_is_guilty(const void *row, const void *guilty)
> +static bool meta_row_is_guilty(const void *row, const void *addr)
> {
> - return (row <= guilty) && (guilty < row + META_BYTES_PER_ROW);
> + return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
> }
>
> -static int shadow_pointer_offset(const void *row, const void *shadow)
> +static int meta_pointer_offset(const void *row, const void *addr)
> {
> - /* The length of ">ff00ff00ff00ff00: " is
> - * 3 + (BITS_PER_LONG/8)*2 chars.
> + /*
> + * Memory state around the buggy address:
> + * ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
> + * ...
> + *
> + * The length of ">ff00ff00ff00ff00: " is
> + * 3 + (BITS_PER_LONG / 8) * 2 chars.
> + * The length of each granule metadata is 2 bytes
> + * plus 1 byte for space.
> */
> - return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
> - (shadow - row) / META_BYTES_PER_BLOCK + 1;
> + return 3 + (BITS_PER_LONG / 8) * 2 +
> + (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
> }
>
> static void print_memory_metadata(const void *addr)
> {
> int i;
> - const void *shadow = kasan_mem_to_shadow(addr);
> - const void *shadow_row;
> + void *row;
>
> - shadow_row = (void *)round_down((unsigned long)shadow,
> - META_BYTES_PER_ROW)
> - - META_ROWS_AROUND_ADDR * META_BYTES_PER_ROW;
> + row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
> + - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
>
> pr_err("Memory state around the buggy address:\n");
>
> for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
> - const void *kaddr = kasan_shadow_to_mem(shadow_row);
> - char buffer[4 + (BITS_PER_LONG/8)*2];
> - char shadow_buf[META_BYTES_PER_ROW];
> + char buffer[4 + (BITS_PER_LONG / 8) * 2];
> + char metadata[META_BYTES_PER_ROW];
>
> snprintf(buffer, sizeof(buffer),
> - (i == 0) ? ">%px: " : " %px: ", kaddr);
> + (i == 0) ? ">%px: " : " %px: ", row);
> +
> /*
> * We should not pass a shadow pointer to generic
> * function, because generic functions may try to
> * access kasan mapping for the passed address.
> */
> - memcpy(shadow_buf, shadow_row, META_BYTES_PER_ROW);
> + metadata_fetch_row(&metadata[0], row);
> +
> print_hex_dump(KERN_ERR, buffer,
> DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
> - shadow_buf, META_BYTES_PER_ROW, 0);
> + metadata, META_BYTES_PER_ROW, 0);
>
> - if (row_is_guilty(shadow_row, shadow))
> - pr_err("%*c\n",
> - shadow_pointer_offset(shadow_row, shadow),
> - '^');
> + if (meta_row_is_guilty(row, addr))
> + pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
>
> - shadow_row += META_BYTES_PER_ROW;
> + row += META_MEM_BYTES_PER_ROW;
> }
> }
>
> diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c
> index 16ed550850e9..8a9c889872da 100644
> --- a/mm/kasan/report_generic.c
> +++ b/mm/kasan/report_generic.c
> @@ -123,6 +123,11 @@ const char *get_bug_type(struct kasan_access_info *info)
> return get_wild_bug_type(info);
> }
>
> +void metadata_fetch_row(char *buffer, void *row)
> +{
> + memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
I think it is important to use __memcpy() instead of memcpy() in KASAN
runtime to avoid calling instrumented code.
> +}
> +
> #if CONFIG_KASAN_STACK
> static bool __must_check tokenize_frame_descr(const char **frame_descr,
> char *token, size_t max_tok_len,
> diff --git a/mm/kasan/report_sw_tags.c b/mm/kasan/report_sw_tags.c
> index c87d5a343b4e..add2dfe6169c 100644
> --- a/mm/kasan/report_sw_tags.c
> +++ b/mm/kasan/report_sw_tags.c
> @@ -80,6 +80,11 @@ void *find_first_bad_addr(void *addr, size_t size)
> return p;
> }
>
> +void metadata_fetch_row(char *buffer, void *row)
> +{
> + memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
Ditto.
> +}
> +
> void print_tags(u8 addr_tag, const void *addr)
> {
> u8 *shadow = (u8 *)kasan_mem_to_shadow(addr);
> --
> 2.29.2.222.g5d2a92d10f8-goog
>
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
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