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SubjectRe: [PATCH] drm/i2c/ch7006: fix a possible null pointer dereference
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On Sat, 2023-10-07 at 11:17 +0800, Ma Ke wrote:
> In ch7006_encoder_get_modes(), the return value of drm_mode_duplicate()
> is assigned to mode, which will lead to a NULL pointer dereference
> on failure of drm_mode_duplicate(). Add a check to avoid npd.
>
> Signed-off-by: Ma Ke <make_ruc2021@163.com>
> ---
> drivers/gpu/drm/i2c/ch7006_drv.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i2c/ch7006_drv.c b/drivers/gpu/drm/i2c/ch7006_drv.c
> index 131512a5f3bd..27c2f02f5b43 100644
> --- a/drivers/gpu/drm/i2c/ch7006_drv.c
> +++ b/drivers/gpu/drm/i2c/ch7006_drv.c
> @@ -236,8 +236,10 @@ static int ch7006_encoder_get_modes(struct drm_encoder *encoder,
> ~mode->valid_norms & 1<<priv->norm)
> continue;
>
> - drm_mode_probed_add(connector,
> - drm_mode_duplicate(encoder->dev, &mode->mode));
> + struct drm_display_mode *encoder_mode;
> + encoder_mode = drm_mode_duplicate(encoder->dev, &mode->mode);

I think the kernel prefers to have variable declaration at the top of the
scope, and as well: this breaks things because you don't add back the
drm_mode_probed_add() call.

> + if (!mode)
> + continue;
>
> n++;
> }

--
Cheers,
Lyude Paul (she/her)
Software Engineer at Red Hat

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