linux-kernel - Re: [PATCH v2 1/9] kasan: introduce helper functions for determining bug type

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Message-ID: <CAG_fn=XKq3tTEf_kg6uoTX2MXfP6AYhe3_QiE9oe1VRnTLk1tA@mail.gmail.com>
Date:   Thu, 2 Mar 2017 18:19:35 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/9] kasan: introduce helper functions for determining
 bug type

On Thu, Mar 2, 2017 at 2:48 PM, Andrey Konovalov <andreyknvl@...gle.com> wrote:
> Introduce get_shadow_bug_type() function, which determines bug type
> based on the shadow value for a particular kernel address.
> Introduce get_wild_bug_type() function, which determines bug type
> for addresses which don't have a corresponding shadow value.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> ---
>  mm/kasan/report.c | 40 ++++++++++++++++++++++++++++++----------
>  1 file changed, 30 insertions(+), 10 deletions(-)
>
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index f479365530b6..2790b4cadfa3 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -49,7 +49,13 @@ static const void *find_first_bad_addr(const void *addr, size_t size)
>         return first_bad_addr;
>  }
>
> -static void print_error_description(struct kasan_access_info *info)
> +static bool addr_has_shadow(struct kasan_access_info *info)
> +{
> +       return (info->access_addr >=
> +               kasan_shadow_to_mem((void *)KASAN_SHADOW_START));
> +}
> +
> +static const char *get_shadow_bug_type(struct kasan_access_info *info)
>  {
>         const char *bug_type = "unknown-crash";
>         u8 *shadow_addr;
> @@ -96,6 +102,27 @@ static void print_error_description(struct kasan_access_info *info)
>                 break;
>         }
>
> +       return bug_type;
> +}
> +
> +const char *get_wild_bug_type(struct kasan_access_info *info)
> +{
> +       const char *bug_type = "unknown-crash";
You don't seem to need "unknown-crash" here.
> +       if ((unsigned long)info->access_addr < PAGE_SIZE)
> +               bug_type = "null-ptr-deref";
> +       else if ((unsigned long)info->access_addr < TASK_SIZE)
> +               bug_type = "user-memory-access";
> +       else
> +               bug_type = "wild-memory-access";
> +
> +       return bug_type;
> +}
> +
> +static void print_error_description(struct kasan_access_info *info)
> +{
> +       const char *bug_type = get_shadow_bug_type(info);
> +
>         pr_err("BUG: KASAN: %s in %pS at addr %p\n",
>                 bug_type, (void *)info->ip,
>                 info->access_addr);
> @@ -265,18 +292,11 @@ static void print_shadow_for_address(const void *addr)
>  static void kasan_report_error(struct kasan_access_info *info)
>  {
>         unsigned long flags;
> -       const char *bug_type;
>
>         kasan_start_report(&flags);
>
> -       if (info->access_addr <
> -                       kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) {
> -               if ((unsigned long)info->access_addr < PAGE_SIZE)
> -                       bug_type = "null-ptr-deref";
> -               else if ((unsigned long)info->access_addr < TASK_SIZE)
> -                       bug_type = "user-memory-access";
> -               else
> -                       bug_type = "wild-memory-access";
> +       if (!addr_has_shadow(info)) {
> +               const char *bug_type = get_wild_bug_type(info);
>                 pr_err("BUG: KASAN: %s on address %p\n",
>                         bug_type, info->access_addr);
>                 pr_err("%s of size %zu by task %s/%d\n",
> --
> 2.12.0.rc1.440.g5b76565f74-goog
>



-- 
Alexander Potapenko
Software Engineer

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