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Thu, 01 Oct 2020 10:54:07 -0700 (PDT) Date: Thu, 1 Oct 2020 19:54:02 +0200 From: elver@google.com To: Andrey Konovalov Cc: Dmitry Vyukov , Vincenzo Frascino , Catalin Marinas , kasan-dev@googlegroups.com, Andrey Ryabinin , Alexander Potapenko , Evgenii Stepanov , Elena Petrova , Branislav Rankov , Kevin Brodsky , Will Deacon , Andrew Morton , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 20/39] kasan: separate metadata_fetch_row for each mode Message-ID: <20201001175402.GP4162920@elver.google.com> References: <494045645c31b7f9298851118cb0b7f8964ac0f4.1600987622.git.andreyknvl@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <494045645c31b7f9298851118cb0b7f8964ac0f4.1600987622.git.andreyknvl@google.com> User-Agent: Mutt/1.14.5 (2020-06-23) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Sep 25, 2020 at 12:50AM +0200, Andrey Konovalov wrote: > This is a preparatory commit for the upcoming addition of a new hardware > tag-based (MTE-based) KASAN mode. Not sure why I've only noticed this now, but all these patches seem to say "This is a preparatory commit" -- I don't think "commit" is applicable, and "This .. patch" is discouraged. Maybe just change it to say "This is to prepare for the upcoming ..." after the below paragraph? > 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. (i.e. move it here) > No functional changes for software modes. > > Signed-off-by: Andrey Konovalov > Signed-off-by: Vincenzo Frascino Other than that, Reviewed-by: Marco Elver > --- > 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 0bf669fad345..50b59c8f8be2 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); > > #ifdef CONFIG_KASAN_STACK_ENABLE > void print_address_stack_frame(const void *addr); > diff --git a/mm/kasan/report.c b/mm/kasan/report.c > index 13b27675a696..3924127b4786 100644 > --- a/mm/kasan/report.c > +++ b/mm/kasan/report.c > @@ -31,12 +31,6 @@ > #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 > @@ -236,55 +230,59 @@ 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 ff067071cd28..de7a85c83106 100644 > --- a/mm/kasan/report_generic.c > +++ b/mm/kasan/report_generic.c > @@ -122,6 +122,11 @@ 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); > +} > + > #ifdef CONFIG_KASAN_STACK_ENABLE > 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); > +} > + > void print_tags(u8 addr_tag, const void *addr) > { > u8 *shadow = (u8 *)kasan_mem_to_shadow(addr); > -- > 2.28.0.681.g6f77f65b4e-goog >