Re: [PATCH 1/6] tests/9p: add 'use-after-unlink' test

[Greg Kurz <groug@kaod.org>]

Hi Christian,

On Wed, 21 Feb 2024 15:13:13 +0100
Christian Schoenebeck <qemu_oss@crudebyte.com> wrote:

> After removing a file from the file system, we should still be able to
> work with the file if we already had it open before removal.
> 
> As a first step we verify that it is possible to write to an unlinked
> file, as this is what already works. This test is extended later on
> after having fixed other use cases after unlink that are not working
> yet.
> 
> Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
> ---

Test looks good but make sure it is merged last to preserve bisect.

Reviewed-by: Greg Kurz <groug@kaod.org>

>  tests/qtest/virtio-9p-test.c | 41 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/tests/qtest/virtio-9p-test.c b/tests/qtest/virtio-9p-test.c
> index 3c8cd235cf..f6d7400a87 100644
> --- a/tests/qtest/virtio-9p-test.c
> +++ b/tests/qtest/virtio-9p-test.c
> @@ -693,6 +693,45 @@ static void fs_unlinkat_hardlink(void *obj, void *data,
>      g_assert(stat(real_file, &st_real) == 0);
>  }
>  
> +static void fs_use_after_unlink(void *obj, void *data,
> +                                QGuestAllocator *t_alloc)
> +{
> +    QVirtio9P *v9p = obj;
> +    v9fs_set_allocator(t_alloc);
> +    static const uint32_t write_count = P9_MAX_SIZE / 2;
> +    g_autofree char *real_file = virtio_9p_test_path("09/doa_file");
> +    g_autofree char *buf = g_malloc0(write_count);
> +    struct stat st_file;
> +    uint32_t fid_file;
> +    uint32_t count;
> +
> +    tattach({ .client = v9p });
> +
> +    /* create a file "09/doa_file" and make sure it exists and is regular */
> +    tmkdir({ .client = v9p, .atPath = "/", .name = "09" });
> +    tlcreate({ .client = v9p, .atPath = "09", .name = "doa_file" });
> +    g_assert(stat(real_file, &st_file) == 0);
> +    g_assert((st_file.st_mode & S_IFMT) == S_IFREG);
> +
> +    /* request a FID for that regular file that we can work with next */
> +    fid_file = twalk({
> +        .client = v9p, .fid = 0, .path = "09/doa_file"
> +    }).newfid;
> +    g_assert(fid_file != 0);
> +
> +    /* now first open the file in write mode before ... */
> +    tlopen({ .client = v9p, .fid = fid_file, .flags = O_WRONLY });
> +    /* ... removing the file from file system */
> +    tunlinkat({ .client = v9p, .atPath = "09", .name = "doa_file" });
> +
> +    /* file is removed, but we still have it open, so this should succeed */
> +    count = twrite({
> +        .client = v9p, .fid = fid_file, .offset = 0, .count = write_count,
> +        .data = buf
> +    }).count;
> +    g_assert_cmpint(count, ==, write_count);
> +}
> +
>  static void cleanup_9p_local_driver(void *data)
>  {
>      /* remove previously created test dir when test is completed */
> @@ -758,6 +797,8 @@ static void register_virtio_9p_test(void)
>      qos_add_test("local/hardlink_file", "virtio-9p", fs_hardlink_file, &opts);
>      qos_add_test("local/unlinkat_hardlink", "virtio-9p", fs_unlinkat_hardlink,
>                   &opts);
> +    qos_add_test("local/use_after_unlink", "virtio-9p", fs_use_after_unlink,
> +                 &opts);
>  }
>  
>  libqos_init(register_virtio_9p_test);


Cheers,

-- 
Greg