Re: [PATCH] ALSA: FCP: Fix NULL pointer dereference in interface lookup

[Takashi Iwai]

On Thu, 25 Jun 2026 15:49:33 +0200,
Jiaming Zhang wrote:
> 
> A malformed USB device can provide a vendor-specific interface without
> any endpoint descriptors. fcp_find_fc_interface() currently selects the
> first vendor-specific interface and reads endpoint 0 from it, without
> checking whether the interface actually has any endpoints.
> 
> When bNumEndpoints is zero, no endpoint array is allocated for the parsed
> alternate setting, so get_endpoint(..., 0) yields an invalid endpoint
> descriptor pointer. Dereferencing it through usb_endpoint_num() then
> triggers a NULL pointer dereference.
> 
> Skip vendor-specific interfaces that do not have any endpoints.
> 
> Fixes: 46757a3e7d50 ("ALSA: FCP: Add Focusrite Control Protocol driver")
> Reported-by: Jiaming Zhang <r772577952@xxxxxxxxx>
> Closes: https://lore.kernel.org/lkml/CANypQFb1EHj0xX8bA1WxSOSK-5xca6ZNKzOQcp12=s=puY7VFw@xxxxxxxxxxxxxx/
> Signed-off-by: Jiaming Zhang <r772577952@xxxxxxxxx>

Applied now.  Thanks.


Takashi