[PATCH v2 7/8] drm/bridge: synopsys: dw-dp: Unregister AUX channel on bridge detach

[Cristian Ciocaltea]

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:
>> 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/