Re: [PATCH] drm: Optimized by adding the TV modes attribute

[Ruben Wauters <rubenru09@aol.com>]

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On Mon, 2026-08-17 at 20:37 +0800, Edward Adam Davis wrote:
> When adding gud properties for drm connector within the function
> gud_connector_add_properties(), if the TV modes property is not added
> first, drm_mode_create_tv_properties_legacy() would fail to add the TV
> modes property because the tv_select_subconnector_property has already
> been added.
> 
> This causes gud_connector_property_lookup() to fail when looking for
> the TV modes property (returning NULL), which subsequently triggers
> issue [1] when a NULL property is passed to drm_object_attach_property().
> 
> The fix ensures that within drm_mode_create_tv_properties_legacy(), the
> TV modes property is correctly added regardless of whether the subconnector
> property exists.
> 
> [1]
> Oops: general protection fault, probably for non-canonical address 0xdffffc000000000c: 0000 [#1] SMP KASAN NOPTI
> KASAN: null-ptr-deref in range [0x0000000000000060-0x0000000000000067]
> RIP: 0010:drm_object_attach_property+0x85/0x3b0 drivers/gpu/drm/drm_mode_object.c:240
> Call Trace:
>  gud_connector_add_properties drivers/gpu/drm/gud/gud_connector.c:572 [inline]
>  gud_connector_create drivers/gpu/drm/gud/gud_connector.c:680 [inline]
>  gud_get_connectors+0x86e/0x1700 drivers/gpu/drm/gud/gud_connector.c:717
>  gud_probe+0x17aa/0x1c20 drivers/gpu/drm/gud/gud_drv.c:635
>  
> Fixes: f453ba046074 ("DRM: add mode setting support")
> Reported-by: syzbot+1944765c3659f63d3777@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=1944765c3659f63d3777
> Tested-by: syzbot+1944765c3659f63d3777@syzkaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Acked-by: Ruben Wauters <rubenru09@aol.com>
> ---
>  drivers/gpu/drm/drm_connector.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 11646453aaac..ecbbc967f51f 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -2175,8 +2175,12 @@ int drm_mode_create_tv_properties_legacy(struct drm_device *dev,
>  	struct drm_property *tv_subconnector;
>  	unsigned int i;
>  
> -	if (dev->mode_config.tv_select_subconnector_property)
> +	if (dev->mode_config.tv_select_subconnector_property) {
> +		if (num_modes && !dev->mode_config.legacy_tv_mode_property)
> +			goto other;
> +
>  		return 0;
> +	}
>  
>  	/*
>  	 * Basic connector properties
> @@ -2199,6 +2203,7 @@ int drm_mode_create_tv_properties_legacy(struct drm_device *dev,
>  		goto nomem;
>  	dev->mode_config.tv_subconnector_property = tv_subconnector;
>  
> +other:
>  	/*
>  	 * Other, TV specific properties: margins & TV modes.
>  	 */

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