Hello Heiko,

On 3/26/26 9:28 PM, Heiko Stuebner wrote:

Am Montag, 9. März 2026, 23:44:35 Mitteleuropäische Normalzeit schrieb Cristian Ciocaltea:

quoted

The DisplayPort AUX channel gets initialized and registered during
dw_dp_bind(), but it is never unregistered, which may lead to resource
leaks and/or use-after-free:

[  224.661371] BUG: KASAN: slab-use-after-free in device_is_dependent+0xe0/0x2b0
[  224.662015] Read of size 8 at addr ffff00011aee8550 by task modprobe/658
...
[  224.662796]  device_is_dependent+0xe0/0x2b0
[  224.662802]  device_is_dependent+0x108/0x2b0
[  224.662808]  device_link_add+0x1f8/0x10b0
[  224.662813]  devm_of_phy_get_by_index+0x120/0x200
[  224.662819]  dw_dp_bind+0x34c/0xb10 [dw_dp]
[  224.662830]  dw_dp_rockchip_bind+0x194/0x250 [rockchipdrm]
[  224.662864]  component_bind_all+0x3a8/0x720
[  224.662869]  rockchip_drm_bind+0x120/0x390 [rockchipdrm]
[  224.662899]  try_to_bring_up_aggregate_device+0x76c/0x838
[  224.662904]  component_master_add_with_match+0x1f4/0x230
[  224.662909]  rockchip_drm_platform_probe+0x420/0x538 [rockchipdrm]
[  224.662939]  platform_probe+0xe8/0x168
[  224.662945]  really_probe+0x340/0x828
[  224.662950]  __driver_probe_device+0x2e0/0x350
[  224.662954]  driver_probe_device+0x80/0x140
[  224.662959]  __driver_attach+0x398/0x460
[  224.662964]  bus_for_each_dev+0xe0/0x198
[  224.662968]  driver_attach+0x50/0x68
[  224.662972]  bus_add_driver+0x2a0/0x4c0
[  224.662977]  driver_register+0x294/0x360
[  224.662982]  __platform_driver_register+0x7c/0x98
[  224.662987]  rockchip_drm_init+0xc4/0xff8 [rockchipdrm]
...

Unregister the AUX adapter on bridge detach.

that sounds sort of asymmetrical though. drm_bridge_funcs has attach and
detach callbacks and the component-framework also has bind and unbind
callbacks.

This might cause confusion later on I guess, especially as I don't know
if there could be a bridge attach, after the detach that unregisters the
aux adapter.

Looking at the AnalogixDP for example, it does the the register and
unregister in the bind/unbind callbacks of the core driver.

So I guess the in my eyes cleaner way would be to introduce a
dw_dp_unbind() function and put the aux unregister there?

At least that way, everything would be at the same "level".

You are right.  As a matter of fact exporting the *_unbind() in the library was
my first thought, but for some reason I went with the "auto" approach.

I've just handled this in v3 [1].

Thanks for reviewing and picking the rest of the patches!

Regards,
Cristian

[1] https://lore.kernel.org/all/20260327-drm-rk-fixes-v3-0-fd2e6900c08c@collabora.com/ (local)