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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Mon, 11 May 2020 12:01:14 +0200
Message-ID: <CACT4Y+aC4i8cAVFu2-s82RczWCjYMpPVJLwS0OBLELR9qF8SYg@mail.gmail.com>
Subject: Re: [PATCH v2 0/3] kasan: memorize and print call_rcu stack
To:     Walter Wu <walter-zh.wu@mediatek.com>
Cc:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        Josh Triplett <josh@joshtriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        Joel Fernandes <joel@joelfernandes.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        wsd_upstream <wsd_upstream@mediatek.com>,
        linux-mediatek@lists.infradead.org
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On Mon, May 11, 2020 at 4:24 AM Walter Wu <walter-zh.wu@mediatek.com> wrote:
>
> This patchset improves KASAN reports by making them to have
> call_rcu() call stack information. It is useful for programmers
> to solve use-after-free or double-free memory issue.

Hi Walter,

I am looking at this now.

I've upload the change to gerrit [1]
https://linux-review.googlesource.com/c/linux/kernel/git/torvalds/linux/+/2458

I am not capable enough to meaningfully review such changes in this format...

[1] https://linux.googlesource.com/Documentation


> The KASAN report was as follows(cleaned up slightly):
>
> BUG: KASAN: use-after-free in kasan_rcu_reclaim+0x58/0x60
>
> Freed by task 0:
>  save_stack+0x24/0x50
>  __kasan_slab_free+0x110/0x178
>  kasan_slab_free+0x10/0x18
>  kfree+0x98/0x270
>  kasan_rcu_reclaim+0x1c/0x60
>  rcu_core+0x8b4/0x10f8
>  rcu_core_si+0xc/0x18
>  efi_header_end+0x238/0xa6c
>
> First call_rcu() call stack:
>  save_stack+0x24/0x50
>  kasan_record_callrcu+0xc8/0xd8
>  call_rcu+0x190/0x580
>  kasan_rcu_uaf+0x1d8/0x278
>
> Last call_rcu() call stack:
> (stack is not available)
>
> Generic KASAN will record first and last call_rcu() call stack
> and print two call_rcu() call stack in KASAN report.
>
> This feature doesn't increase the cost of memory consumption. It is
> only suitable for generic KASAN.
>
> [1]https://bugzilla.kernel.org/show_bug.cgi?id=198437
> [2]https://groups.google.com/forum/#!searchin/kasan-dev/better$20stack$20traces$20for$20rcu%7Csort:date/kasan-dev/KQsjT_88hDE/7rNUZprRBgAJ
>
> Changes since v2:
> - remove new config option, default enable it in generic KASAN
> - test this feature in SLAB/SLUB, it is pass.
> - modify macro to be more clearly
> - modify documentation
>
> Walter Wu (3):
> rcu/kasan: record and print call_rcu() call stack
> kasan: record and print the free track
> kasan: update documentation for generic kasan
>
> Documentation/dev-tools/kasan.rst |  6 ++++++
> include/linux/kasan.h             |  2 ++
> kernel/rcu/tree.c                 |  4 ++++
> lib/Kconfig.kasan                 |  2 ++
> mm/kasan/common.c                 | 26 ++++----------------------
> mm/kasan/generic.c                | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
> mm/kasan/kasan.h                  | 23 +++++++++++++++++++++++
> mm/kasan/report.c                 | 47 +++++++++++++++++++++--------------------------
> mm/kasan/tags.c                   | 37 +++++++++++++++++++++++++++++++++++++
> 9 files changed, 149 insertions(+), 48 deletions(-)
>
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