Re: [PATCH v2 RESEND] kunit: debugfs: Handle errors from alloc_string_stream()

Rae Moar
2023-11-30T21:11:35Z

On Mon, Oct 30, 2023 at 6:47 AM Richard Fitzgerald
<rf@opensource.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@google.com>

Thanks!
-Rae

>
> Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
> Reported-by: Dan Carpenter <dan.carpenter@linaro.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
>