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Date: Thu, 16 Jan 2020 13:32:33 +0100
From: Andrey Konovalov <andreyknvl@...gle.com>
To: Kees Cook <keescook@...omium.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Dmitry Vyukov <dvyukov@...gle.com>, 
	Andrey Ryabinin <aryabinin@...tuozzo.com>, Elena Petrova <lenaptr@...gle.com>, 
	Alexander Potapenko <glider@...gle.com>, Dan Carpenter <dan.carpenter@...cle.com>, 
	"Gustavo A. R. Silva" <gustavo@...eddedor.com>, Arnd Bergmann <arnd@...db.de>, 
	Ard Biesheuvel <ard.biesheuvel@...aro.org>, kasan-dev <kasan-dev@...glegroups.com>, 
	Linux Memory Management List <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, 
	kernel-hardening@...ts.openwall.com, syzkaller <syzkaller@...glegroups.com>
Subject: Re: [PATCH v3 6/6] ubsan: Include bug type in report header

On Thu, Jan 16, 2020 at 2:24 AM Kees Cook <keescook@...omium.org> wrote:
>
> When syzbot tries to figure out how to deduplicate bug reports, it
> prefers seeing a hint about a specific bug type (we can do better than
> just "UBSAN"). This lifts the handler reason into the UBSAN report line
> that includes the file path that tripped a check. Unfortunately, UBSAN
> does not provide function names.
>
> Suggested-by: Dmitry Vyukov <dvyukov@...gle.com>
> Link: https://lore.kernel.org/lkml/CACT4Y+bsLJ-wFx_TaXqax3JByUOWB3uk787LsyMVcfW6JzzGvg@mail.gmail.com
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  lib/ubsan.c | 36 +++++++++++++++---------------------
>  1 file changed, 15 insertions(+), 21 deletions(-)
>
> diff --git a/lib/ubsan.c b/lib/ubsan.c
> index 429663eef6a7..057d5375bfc6 100644
> --- a/lib/ubsan.c
> +++ b/lib/ubsan.c
> @@ -45,13 +45,6 @@ static bool was_reported(struct source_location *location)
>         return test_and_set_bit(REPORTED_BIT, &location->reported);
>  }
>
> -static void print_source_location(const char *prefix,
> -                               struct source_location *loc)
> -{
> -       pr_err("%s %s:%d:%d\n", prefix, loc->file_name,
> -               loc->line & LINE_MASK, loc->column & COLUMN_MASK);
> -}
> -
>  static bool suppress_report(struct source_location *loc)
>  {
>         return current->in_ubsan || was_reported(loc);
> @@ -140,13 +133,14 @@ static void val_to_string(char *str, size_t size, struct type_descriptor *type,
>         }
>  }
>
> -static void ubsan_prologue(struct source_location *location)
> +static void ubsan_prologue(struct source_location *loc, const char *reason)
>  {
>         current->in_ubsan++;
>
>         pr_err("========================================"
>                 "========================================\n");
> -       print_source_location("UBSAN: Undefined behaviour in", location);
> +       pr_err("UBSAN: %s in %s:%d:%d\n", reason, loc->file_name,
> +               loc->line & LINE_MASK, loc->column & COLUMN_MASK);
>  }
>
>  static void ubsan_epilogue(void)
> @@ -180,12 +174,12 @@ static void handle_overflow(struct overflow_data *data, void *lhs,
>         if (suppress_report(&data->location))
>                 return;
>
> -       ubsan_prologue(&data->location);
> +       ubsan_prologue(&data->location, type_is_signed(type) ?
> +                       "signed integer overflow" :
> +                       "unsigned integer overflow");
>
>         val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
>         val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
> -       pr_err("%s integer overflow:\n",
> -               type_is_signed(type) ? "signed" : "unsigned");
>         pr_err("%s %c %s cannot be represented in type %s\n",
>                 lhs_val_str,
>                 op,
> @@ -225,7 +219,7 @@ void __ubsan_handle_negate_overflow(struct overflow_data *data,
>         if (suppress_report(&data->location))
>                 return;
>
> -       ubsan_prologue(&data->location);
> +       ubsan_prologue(&data->location, "negation overflow");
>
>         val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
>
> @@ -245,7 +239,7 @@ void __ubsan_handle_divrem_overflow(struct overflow_data *data,
>         if (suppress_report(&data->location))
>                 return;
>
> -       ubsan_prologue(&data->location);
> +       ubsan_prologue(&data->location, "division overflow");
>
>         val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
>
> @@ -264,7 +258,7 @@ static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
>         if (suppress_report(data->location))
>                 return;
>
> -       ubsan_prologue(data->location);
> +       ubsan_prologue(data->location, "NULL pointer dereference");

Not crucially important, but I think it makes sense to use the
single-word-with-hyphens bug type format like in KASAN here, e.g.
null-ptr-deref, misaligned-access, etc.


>
>         pr_err("%s null pointer of type %s\n",
>                 type_check_kinds[data->type_check_kind],
> @@ -279,7 +273,7 @@ static void handle_misaligned_access(struct type_mismatch_data_common *data,
>         if (suppress_report(data->location))
>                 return;
>
> -       ubsan_prologue(data->location);
> +       ubsan_prologue(data->location, "misaligned access");
>
>         pr_err("%s misaligned address %p for type %s\n",
>                 type_check_kinds[data->type_check_kind],
> @@ -295,7 +289,7 @@ static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
>         if (suppress_report(data->location))
>                 return;
>
> -       ubsan_prologue(data->location);
> +       ubsan_prologue(data->location, "object size mismatch");
>         pr_err("%s address %p with insufficient space\n",
>                 type_check_kinds[data->type_check_kind],
>                 (void *) ptr);
> @@ -354,7 +348,7 @@ void __ubsan_handle_out_of_bounds(struct out_of_bounds_data *data, void *index)
>         if (suppress_report(&data->location))
>                 return;
>
> -       ubsan_prologue(&data->location);
> +       ubsan_prologue(&data->location, "array index out of bounds");
>
>         val_to_string(index_str, sizeof(index_str), data->index_type, index);
>         pr_err("index %s is out of range for type %s\n", index_str,
> @@ -375,7 +369,7 @@ void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
>         if (suppress_report(&data->location))
>                 goto out;
>
> -       ubsan_prologue(&data->location);
> +       ubsan_prologue(&data->location, "shift out of bounds");
>
>         val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
>         val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
> @@ -407,7 +401,7 @@ EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
>
>  void __ubsan_handle_builtin_unreachable(struct unreachable_data *data)
>  {
> -       ubsan_prologue(&data->location);
> +       ubsan_prologue(&data->location, "unreachable");
>         pr_err("calling __builtin_unreachable()\n");
>         ubsan_epilogue();
>         panic("can't return from __builtin_unreachable()");
> @@ -422,7 +416,7 @@ void __ubsan_handle_load_invalid_value(struct invalid_value_data *data,
>         if (suppress_report(&data->location))
>                 return;
>
> -       ubsan_prologue(&data->location);
> +       ubsan_prologue(&data->location, "invalid load");
>
>         val_to_string(val_str, sizeof(val_str), data->type, val);
>
> --
> 2.20.1
>
> --
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