Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220309083753.1561921-1-liupeng256@huawei.com> <20220309083753.1561921-2-liupeng256@huawei.com>
In-Reply-To: <20220309083753.1561921-2-liupeng256@huawei.com>
From:   Brendan Higgins <brendanhiggins@google.com>
Date:   Thu, 10 Mar 2022 03:08:59 -0500
Message-ID: <CAFd5g466XMWRszdn=Wdg4GXNv=KR-CZmWYZ0j0bG7_1QXtu-LQ@mail.gmail.com>
Subject: Re: [PATCH v2 1/3] kunit: fix UAF when run kfence test case test_gfpzero
To:     Peng Liu <liupeng256@huawei.com>
Cc:     glider@google.com, elver@google.com, dvyukov@google.com,
        akpm@linux-foundation.org, linux-kselftest@vger.kernel.org,
        kunit-dev@googlegroups.com, linux-kernel@vger.kernel.org,
        kasan-dev@googlegroups.com, linux-mm@kvack.org,
        wangkefeng.wang@huawei.com
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, Mar 9, 2022 at 3:19 AM 'Peng Liu' via KUnit Development
<kunit-dev@googlegroups.com> wrote:
>
> Kunit will create a new thread to run an actual test case, and the
> main process will wait for the completion of the actual test thread
> until overtime. The variable "struct kunit test" has local property
> in function kunit_try_catch_run, and will be used in the test case
> thread. Task kunit_try_catch_run will free "struct kunit test" when
> kunit runs overtime, but the actual test case is still run and an
> UAF bug will be triggered.
>
> The above problem has been both observed in a physical machine and
> qemu platform when running kfence kunit tests. The problem can be
> triggered when setting CONFIG_KFENCE_NUM_OBJECTS = 65535. Under
> this setting, the test case test_gfpzero will cost hours and kunit
> will run to overtime. The follows show the panic log.
>
>   BUG: unable to handle page fault for address: ffffffff82d882e9
>
>   Call Trace:
>    kunit_log_append+0x58/0xd0
>    ...
>    test_alloc.constprop.0.cold+0x6b/0x8a [kfence_test]
>    test_gfpzero.cold+0x61/0x8ab [kfence_test]
>    kunit_try_run_case+0x4c/0x70
>    kunit_generic_run_threadfn_adapter+0x11/0x20
>    kthread+0x166/0x190
>    ret_from_fork+0x22/0x30
>   Kernel panic - not syncing: Fatal exception
>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
>   Ubuntu-1.8.2-1ubuntu1 04/01/2014
>
> To solve this problem, the test case thread should be stopped when
> the kunit frame runs overtime. The stop signal will send in function
> kunit_try_catch_run, and test_gfpzero will handle it.
>
> Signed-off-by: Peng Liu <liupeng256@huawei.com>

Thanks for taking care of this.

Reviewed-by: Brendan Higgins <brendanhiggins@google.com>