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From:   Andrey Konovalov <andreyknvl@gmail.com>
Date:   Sun, 11 Sep 2022 13:48:45 +0200
Message-ID: <CA+fCnZfgwjT+Yzxpz-pesqVhitq13Z5aypaXjFodZyCDLr9d6Q@mail.gmail.com>
Subject: Re: [PATCH] kasan: better invalid/double-free report header
To:     andrey.konovalov@linux.dev
Cc:     Marco Elver <elver@google.com>,
        Alexander Potapenko <glider@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrey Konovalov <andreyknvl@google.com>
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On Sun, Sep 11, 2022 at 1:25 AM <andrey.konovalov@linux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@google.com>
>
> Update the report header for invalid- and double-free bugs to contain
> the address being freed:
>
> BUG: KASAN: invalid-free in kfree+0x280/0x2a8
> Free of addr ffff00000beac001 by task kunit_try_catch/99
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

Forgot to mention: this goes on top of the "kasan: switch tag-based
modes to stack ring from per-object metadata" series.

> ---
>  mm/kasan/report.c         | 23 ++++++++++++++++-------
>  mm/kasan/report_generic.c |  3 ++-
>  mm/kasan/report_tags.c    |  2 +-
>  3 files changed, 19 insertions(+), 9 deletions(-)
>
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 39e8e5a80b82..df3602062bfd 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -175,17 +175,14 @@ static void end_report(unsigned long *flags, void *addr)
>
>  static void print_error_description(struct kasan_report_info *info)
>  {
> -       if (info->type == KASAN_REPORT_INVALID_FREE) {
> -               pr_err("BUG: KASAN: invalid-free in %pS\n", (void *)info->ip);
> -               return;
> -       }
> +       pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip);
>
> -       if (info->type == KASAN_REPORT_DOUBLE_FREE) {
> -               pr_err("BUG: KASAN: double-free in %pS\n", (void *)info->ip);
> +       if (info->type != KASAN_REPORT_ACCESS) {
> +               pr_err("Free of addr %px by task %s/%d\n",
> +                       info->access_addr, current->comm, task_pid_nr(current));
>                 return;
>         }
>
> -       pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip);
>         if (info->access_size)
>                 pr_err("%s of size %zu at addr %px by task %s/%d\n",
>                         info->is_write ? "Write" : "Read", info->access_size,
> @@ -420,6 +417,18 @@ static void complete_report_info(struct kasan_report_info *info)
>         } else
>                 info->cache = info->object = NULL;
>
> +       switch (info->type) {
> +       case KASAN_REPORT_INVALID_FREE:
> +               info->bug_type = "invalid-free";
> +               break;
> +       case KASAN_REPORT_DOUBLE_FREE:
> +               info->bug_type = "double-free";
> +               break;
> +       default:
> +               /* bug_type filled in by kasan_complete_mode_report_info. */
> +               break;
> +       }
> +
>         /* Fill in mode-specific report info fields. */
>         kasan_complete_mode_report_info(info);
>  }
> diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c
> index 087c1d8c8145..043c94b04605 100644
> --- a/mm/kasan/report_generic.c
> +++ b/mm/kasan/report_generic.c
> @@ -132,7 +132,8 @@ void kasan_complete_mode_report_info(struct kasan_report_info *info)
>         struct kasan_alloc_meta *alloc_meta;
>         struct kasan_free_meta *free_meta;
>
> -       info->bug_type = get_bug_type(info);
> +       if (!info->bug_type)
> +               info->bug_type = get_bug_type(info);
>
>         if (!info->cache || !info->object)
>                 return;
> diff --git a/mm/kasan/report_tags.c b/mm/kasan/report_tags.c
> index d3510424d29b..ecede06ef374 100644
> --- a/mm/kasan/report_tags.c
> +++ b/mm/kasan/report_tags.c
> @@ -37,7 +37,7 @@ void kasan_complete_mode_report_info(struct kasan_report_info *info)
>         bool is_free;
>         bool alloc_found = false, free_found = false;
>
> -       if (!info->cache || !info->object) {
> +       if ((!info->cache || !info->object) && !info->bug_type) {
>                 info->bug_type = get_common_bug_type(info);
>                 return;
>         }
> --
> 2.25.1
>