On Wed, 05 Mar 2025, Wentao Liang <vulab@xxxxxxxxxxx> wrote:
> The return values of `drm_edid_dup()` and `drm_edid_read_ddc()` must
> be checked in `tegra_output_connector_get_modes()` to prevent NULL
> pointer dereferences. If either function fails, the function should
> immediately return 0, indicating that no display modes can be retrieved.
No. It works as designed, and drm_edid_connector_update() and
cec_notifier_set_phys_addr() *must* be called with NULL drm_edid in case
of failure.
> A proper implementation can be found in `vidi_get_modes()`, where the
> return values are carefully validated, and the function returns 0 upon
> failure.
That case is slightly different, as it doesn't actually access the
display at that point, but it wouldn't be wrong to skip the early
!drm_edid check there too.
> Fixes: 98365ca74cbf ("drm/tegra: convert to struct drm_edid")
When you claim to fix a commit, it's encouraged to Cc: the author and
possibly reviewers of said commit.
BR,
Jani.
> Cc: stable@xxxxxxxxxxxxxxx # 6.12+
> Signed-off-by: Wentao Liang <vulab@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/tegra/output.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/tegra/output.c b/drivers/gpu/drm/tegra/output.c
> index 49e4f63a5550..360c4f83a4f8 100644
> --- a/drivers/gpu/drm/tegra/output.c
> +++ b/drivers/gpu/drm/tegra/output.c
> @@ -39,6 +39,9 @@ int tegra_output_connector_get_modes(struct drm_connector *connector)
> else if (output->ddc)
> drm_edid = drm_edid_read_ddc(connector, output->ddc);
>
> + if (!drm_edid)
> + return 0;
> +
> drm_edid_connector_update(connector, drm_edid);
> cec_notifier_set_phys_addr(output->cec,
> connector->display_info.source_physical_address);
--
Jani Nikula, Intel
