Re: [PATCH] ALSA: usb-audio: avoid kobject path lookup in DualSense match

[Takashi Iwai <tiwai@suse.de>]

On Wed, 24 Jun 2026 16:37:23 +0200,
Darvell Long wrote:
> 
> The DualSense jack-detection input handler verifies that a matching input
> device belongs to the same physical controller by building kobject path
> strings for both the input device and the USB audio device, then comparing
> the path prefix.
> 
> This was observed when a weak physical connection caused the controller
> to rapidly disconnect and reconnect. During that repeated hotplug,
> snd_dualsense_ih_match() can run while the controller's USB device is
> being disconnected. kobject_get_path() walks ancestor kobjects and
> dereferences their names; if the USB device kobject name is no longer
> valid, this can fault in strlen():
> 
>   RIP: 0010:strlen+0x10/0x30
>   Call Trace:
>    kobject_get_path+0x34/0x150
>    snd_dualsense_ih_match+0x49/0xd0 [snd_usb_audio]
>    input_register_device+0x566/0x6a0
>    ps_probe+0xb89/0x1590 [hid_playstation]
> 
> The same ownership check can be done without building kobject path
> strings. The input device is parented below the HID device, USB interface
> and USB device, so walking the input device parent chain and comparing
> against the mixer USB device preserves the check without dereferencing
> kobject names during disconnect.
> 
> Fixes: 79d561c4ec04 ("ALSA: usb-audio: Add mixer quirk for Sony DualSense PS5")
> Cc: <stable@vger.kernel.org>
> Assisted-by: Cute:gpt-5.5
> Signed-off-by: Darvell Long <contact@darvell.me>

Thanks, applied now.


Takashi