Re: [PATCH v9 14/44] kasan: decode stack frame only with KASAN_STACK_ENABLE

[Alexander Potapenko <glider@google.com>]

On Tue, Nov 10, 2020 at 11:11 PM Andrey Konovalov <andreyknvl@google.com> wrote:
>
> Decoding routines aren't needed when CONFIG_KASAN_STACK_ENABLE is not
> enabled. Currently only generic KASAN mode implements stack error
> reporting.
>
> No functional changes for software modes.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>

> ---
> Change-Id: I084e3214f2b40dc0bef7c5a9fafdc6f5c42b06a2
> ---
>  mm/kasan/kasan.h          |   6 ++
>  mm/kasan/report.c         | 162 --------------------------------------
>  mm/kasan/report_generic.c | 162 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 168 insertions(+), 162 deletions(-)
>
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 3eff57e71ff5..d0cf61d4d70d 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -169,6 +169,12 @@ 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);
>
> +#if defined(CONFIG_KASAN_GENERIC) && CONFIG_KASAN_STACK
> +void print_address_stack_frame(const void *addr);
> +#else
> +static inline void print_address_stack_frame(const void *addr) { }
> +#endif
> +
>  bool kasan_report(unsigned long addr, size_t size,
>                 bool is_write, unsigned long ip);
>  void kasan_report_invalid_free(void *object, unsigned long ip);
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index fff0c7befbfe..b18d193f7f58 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -211,168 +211,6 @@ static inline bool init_task_stack_addr(const void *addr)
>                         sizeof(init_thread_union.stack));
>  }
>
> -static bool __must_check tokenize_frame_descr(const char **frame_descr,
> -                                             char *token, size_t max_tok_len,
> -                                             unsigned long *value)
> -{
> -       const char *sep = strchr(*frame_descr, ' ');
> -
> -       if (sep == NULL)
> -               sep = *frame_descr + strlen(*frame_descr);
> -
> -       if (token != NULL) {
> -               const size_t tok_len = sep - *frame_descr;
> -
> -               if (tok_len + 1 > max_tok_len) {
> -                       pr_err("KASAN internal error: frame description too long: %s\n",
> -                              *frame_descr);
> -                       return false;
> -               }
> -
> -               /* Copy token (+ 1 byte for '\0'). */
> -               strlcpy(token, *frame_descr, tok_len + 1);
> -       }
> -
> -       /* Advance frame_descr past separator. */
> -       *frame_descr = sep + 1;
> -
> -       if (value != NULL && kstrtoul(token, 10, value)) {
> -               pr_err("KASAN internal error: not a valid number: %s\n", token);
> -               return false;
> -       }
> -
> -       return true;
> -}
> -
> -static void print_decoded_frame_descr(const char *frame_descr)
> -{
> -       /*
> -        * We need to parse the following string:
> -        *    "n alloc_1 alloc_2 ... alloc_n"
> -        * where alloc_i looks like
> -        *    "offset size len name"
> -        * or "offset size len name:line".
> -        */
> -
> -       char token[64];
> -       unsigned long num_objects;
> -
> -       if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
> -                                 &num_objects))
> -               return;
> -
> -       pr_err("\n");
> -       pr_err("this frame has %lu %s:\n", num_objects,
> -              num_objects == 1 ? "object" : "objects");
> -
> -       while (num_objects--) {
> -               unsigned long offset;
> -               unsigned long size;
> -
> -               /* access offset */
> -               if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
> -                                         &offset))
> -                       return;
> -               /* access size */
> -               if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
> -                                         &size))
> -                       return;
> -               /* name length (unused) */
> -               if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL))
> -                       return;
> -               /* object name */
> -               if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
> -                                         NULL))
> -                       return;
> -
> -               /* Strip line number; without filename it's not very helpful. */
> -               strreplace(token, ':', '\0');
> -
> -               /* Finally, print object information. */
> -               pr_err(" [%lu, %lu) '%s'", offset, offset + size, token);
> -       }
> -}
> -
> -static bool __must_check get_address_stack_frame_info(const void *addr,
> -                                                     unsigned long *offset,
> -                                                     const char **frame_descr,
> -                                                     const void **frame_pc)
> -{
> -       unsigned long aligned_addr;
> -       unsigned long mem_ptr;
> -       const u8 *shadow_bottom;
> -       const u8 *shadow_ptr;
> -       const unsigned long *frame;
> -
> -       BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
> -
> -       /*
> -        * NOTE: We currently only support printing frame information for
> -        * accesses to the task's own stack.
> -        */
> -       if (!object_is_on_stack(addr))
> -               return false;
> -
> -       aligned_addr = round_down((unsigned long)addr, sizeof(long));
> -       mem_ptr = round_down(aligned_addr, KASAN_GRANULE_SIZE);
> -       shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
> -       shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));
> -
> -       while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
> -               shadow_ptr--;
> -               mem_ptr -= KASAN_GRANULE_SIZE;
> -       }
> -
> -       while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
> -               shadow_ptr--;
> -               mem_ptr -= KASAN_GRANULE_SIZE;
> -       }
> -
> -       if (shadow_ptr < shadow_bottom)
> -               return false;
> -
> -       frame = (const unsigned long *)(mem_ptr + KASAN_GRANULE_SIZE);
> -       if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
> -               pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n",
> -                      frame[0]);
> -               return false;
> -       }
> -
> -       *offset = (unsigned long)addr - (unsigned long)frame;
> -       *frame_descr = (const char *)frame[1];
> -       *frame_pc = (void *)frame[2];
> -
> -       return true;
> -}
> -
> -static void print_address_stack_frame(const void *addr)
> -{
> -       unsigned long offset;
> -       const char *frame_descr;
> -       const void *frame_pc;
> -
> -       if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
> -               return;
> -
> -       if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
> -                                         &frame_pc))
> -               return;
> -
> -       /*
> -        * get_address_stack_frame_info only returns true if the given addr is
> -        * on the current task's stack.
> -        */
> -       pr_err("\n");
> -       pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n",
> -              addr, current->comm, task_pid_nr(current), offset);
> -       pr_err(" %pS\n", frame_pc);
> -
> -       if (!frame_descr)
> -               return;
> -
> -       print_decoded_frame_descr(frame_descr);
> -}
> -
>  static void print_address_description(void *addr, u8 tag)
>  {
>         struct page *page = kasan_addr_to_page(addr);
> diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c
> index 7d5b9e5c7cfe..b543a1ed6078 100644
> --- a/mm/kasan/report_generic.c
> +++ b/mm/kasan/report_generic.c
> @@ -16,6 +16,7 @@
>  #include <linux/mm.h>
>  #include <linux/printk.h>
>  #include <linux/sched.h>
> +#include <linux/sched/task_stack.h>
>  #include <linux/slab.h>
>  #include <linux/stackdepot.h>
>  #include <linux/stacktrace.h>
> @@ -122,6 +123,167 @@ const char *get_bug_type(struct kasan_access_info *info)
>         return get_wild_bug_type(info);
>  }
>
> +#if CONFIG_KASAN_STACK
> +static bool __must_check tokenize_frame_descr(const char **frame_descr,
> +                                             char *token, size_t max_tok_len,
> +                                             unsigned long *value)
> +{
> +       const char *sep = strchr(*frame_descr, ' ');
> +
> +       if (sep == NULL)
> +               sep = *frame_descr + strlen(*frame_descr);
> +
> +       if (token != NULL) {
> +               const size_t tok_len = sep - *frame_descr;
> +
> +               if (tok_len + 1 > max_tok_len) {
> +                       pr_err("KASAN internal error: frame description too long: %s\n",
> +                              *frame_descr);
> +                       return false;
> +               }
> +
> +               /* Copy token (+ 1 byte for '\0'). */
> +               strlcpy(token, *frame_descr, tok_len + 1);
> +       }
> +
> +       /* Advance frame_descr past separator. */
> +       *frame_descr = sep + 1;
> +
> +       if (value != NULL && kstrtoul(token, 10, value)) {
> +               pr_err("KASAN internal error: not a valid number: %s\n", token);
> +               return false;
> +       }
> +
> +       return true;
> +}
> +
> +static void print_decoded_frame_descr(const char *frame_descr)
> +{
> +       /*
> +        * We need to parse the following string:
> +        *    "n alloc_1 alloc_2 ... alloc_n"
> +        * where alloc_i looks like
> +        *    "offset size len name"
> +        * or "offset size len name:line".
> +        */
> +
> +       char token[64];
> +       unsigned long num_objects;
> +
> +       if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
> +                                 &num_objects))
> +               return;
> +
> +       pr_err("\n");
> +       pr_err("this frame has %lu %s:\n", num_objects,
> +              num_objects == 1 ? "object" : "objects");
> +
> +       while (num_objects--) {
> +               unsigned long offset;
> +               unsigned long size;
> +
> +               /* access offset */
> +               if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
> +                                         &offset))
> +                       return;
> +               /* access size */
> +               if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
> +                                         &size))
> +                       return;
> +               /* name length (unused) */
> +               if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL))
> +                       return;
> +               /* object name */
> +               if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
> +                                         NULL))
> +                       return;
> +
> +               /* Strip line number; without filename it's not very helpful. */
> +               strreplace(token, ':', '\0');
> +
> +               /* Finally, print object information. */
> +               pr_err(" [%lu, %lu) '%s'", offset, offset + size, token);
> +       }
> +}
> +
> +static bool __must_check get_address_stack_frame_info(const void *addr,
> +                                                     unsigned long *offset,
> +                                                     const char **frame_descr,
> +                                                     const void **frame_pc)
> +{
> +       unsigned long aligned_addr;
> +       unsigned long mem_ptr;
> +       const u8 *shadow_bottom;
> +       const u8 *shadow_ptr;
> +       const unsigned long *frame;
> +
> +       BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
> +
> +       /*
> +        * NOTE: We currently only support printing frame information for
> +        * accesses to the task's own stack.
> +        */
> +       if (!object_is_on_stack(addr))
> +               return false;
> +
> +       aligned_addr = round_down((unsigned long)addr, sizeof(long));
> +       mem_ptr = round_down(aligned_addr, KASAN_GRANULE_SIZE);
> +       shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
> +       shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));
> +
> +       while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
> +               shadow_ptr--;
> +               mem_ptr -= KASAN_GRANULE_SIZE;
> +       }
> +
> +       while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
> +               shadow_ptr--;
> +               mem_ptr -= KASAN_GRANULE_SIZE;
> +       }
> +
> +       if (shadow_ptr < shadow_bottom)
> +               return false;
> +
> +       frame = (const unsigned long *)(mem_ptr + KASAN_GRANULE_SIZE);
> +       if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
> +               pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n",
> +                      frame[0]);
> +               return false;
> +       }
> +
> +       *offset = (unsigned long)addr - (unsigned long)frame;
> +       *frame_descr = (const char *)frame[1];
> +       *frame_pc = (void *)frame[2];
> +
> +       return true;
> +}
> +
> +void print_address_stack_frame(const void *addr)
> +{
> +       unsigned long offset;
> +       const char *frame_descr;
> +       const void *frame_pc;
> +
> +       if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
> +                                         &frame_pc))
> +               return;
> +
> +       /*
> +        * get_address_stack_frame_info only returns true if the given addr is
> +        * on the current task's stack.
> +        */
> +       pr_err("\n");
> +       pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n",
> +              addr, current->comm, task_pid_nr(current), offset);
> +       pr_err(" %pS\n", frame_pc);
> +
> +       if (!frame_descr)
> +               return;
> +
> +       print_decoded_frame_descr(frame_descr);
> +}
> +#endif /* CONFIG_KASAN_STACK */
> +
>  #define DEFINE_ASAN_REPORT_LOAD(size)                     \
>  void __asan_report_load##size##_noabort(unsigned long 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