linux-kernel - Re: [PATCH v2 RESEND] kunit: debugfs: Handle errors from alloc_string

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Message-ID: <CA+GJov5vcRPo30CFYDwRq-iXHqtDtLd2jrmB+y_=BY6o2mZaBA@mail.gmail.com>
Date:   Thu, 30 Nov 2023 16:11:18 -0500
From:   Rae Moar <rmoar@...gle.com>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>
Cc:     brendan.higgins@...ux.dev, davidgow@...gle.com,
        linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, patches@...nsource.cirrus.com,
        Dan Carpenter <dan.carpenter@...aro.org>
Subject: Re: [PATCH v2 RESEND] kunit: debugfs: Handle errors from alloc_string_stream()

On Mon, Oct 30, 2023 at 6:47 AM Richard Fitzgerald
<rf@...nsource.cirrus.com> wrote:
>
> In kunit_debugfs_create_suite() give up and skip creating the debugfs
> file if any of the alloc_string_stream() calls return an error or NULL.
> Only put a value in the log pointer of kunit_suite and kunit_test if it
> is a valid pointer to a log.
>
> This prevents the potential invalid dereference reported by smatch:
>
>  lib/kunit/debugfs.c:115 kunit_debugfs_create_suite() error: 'suite->log'
>         dereferencing possible ERR_PTR()
>  lib/kunit/debugfs.c:119 kunit_debugfs_create_suite() error: 'test_case->log'
>         dereferencing possible ERR_PTR()

Hello!

Thanks for sending the re-sends of these patches! This patch also
looks good to me! I have one comment below but I would still be happy
with the patch as is.

Reviewed-by: Rae Moar <rmoar@...gle.com>

Thanks!
-Rae

>
> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> Fixes: 05e2006ce493 ("kunit: Use string_stream for test log")
> ---
>  lib/kunit/debugfs.c | 30 +++++++++++++++++++++++++-----
>  1 file changed, 25 insertions(+), 5 deletions(-)
>
> diff --git a/lib/kunit/debugfs.c b/lib/kunit/debugfs.c
> index 270d185737e6..9d167adfa746 100644
> --- a/lib/kunit/debugfs.c
> +++ b/lib/kunit/debugfs.c
> @@ -109,14 +109,28 @@ static const struct file_operations debugfs_results_fops = {
>  void kunit_debugfs_create_suite(struct kunit_suite *suite)
>  {
>         struct kunit_case *test_case;
> +       struct string_stream *stream;
>
> -       /* Allocate logs before creating debugfs representation. */
> -       suite->log = alloc_string_stream(GFP_KERNEL);
> -       string_stream_set_append_newlines(suite->log, true);
> +       /*
> +        * Allocate logs before creating debugfs representation.
> +        * The suite->log and test_case->log pointer are expected to be NULL
> +        * if there isn't a log, so only set it if the log stream was created
> +        * successfully.
> +        */

I like this new comment. Thanks!

> +       stream = alloc_string_stream(GFP_KERNEL);
> +       if (IS_ERR_OR_NULL(stream))

In response to Dan Carpenter's comment from the last version, I see
the benefits of changing IS_ERR_OR_NULL() to IS_ERR() instead because
"stream" will not be NULL. This would then also be the same as the
check in kunit_alloc_string_stream.

However, I also see the benefit of checking for NULL just in case anyways.

I'm overall happy with either solution but just wanted to bring this up.

> +               return;
> +
> +       string_stream_set_append_newlines(stream, true);
> +       suite->log = stream;
>
>         kunit_suite_for_each_test_case(suite, test_case) {
> -               test_case->log = alloc_string_stream(GFP_KERNEL);
> -               string_stream_set_append_newlines(test_case->log, true);
> +               stream = alloc_string_stream(GFP_KERNEL);
> +               if (IS_ERR_OR_NULL(stream))
> +                       goto err;
> +
> +               string_stream_set_append_newlines(stream, true);
> +               test_case->log = stream;
>         }
>
>         suite->debugfs = debugfs_create_dir(suite->name, debugfs_rootdir);
> @@ -124,6 +138,12 @@ void kunit_debugfs_create_suite(struct kunit_suite *suite)
>         debugfs_create_file(KUNIT_DEBUGFS_RESULTS, S_IFREG | 0444,
>                             suite->debugfs,
>                             suite, &debugfs_results_fops);
> +       return;
> +
> +err:
> +       string_stream_destroy(suite->log);
> +       kunit_suite_for_each_test_case(suite, test_case)
> +               string_stream_destroy(test_case->log);
>  }
>
>  void kunit_debugfs_destroy_suite(struct kunit_suite *suite)
> --
> 2.30.2
>