From: Jiaming Zhang Date: Thu, 25 Jun 2026 13:49:33 +0000 (+0800) Subject: ALSA: FCP: Fix NULL pointer dereference in interface lookup X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e1e31e0ec8a609e17fd2e86b77bc00d9cbb24d7c;p=thirdparty%2Fkernel%2Fstable.git ALSA: FCP: Fix NULL pointer dereference in interface lookup 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 Closes: https://lore.kernel.org/lkml/CANypQFb1EHj0xX8bA1WxSOSK-5xca6ZNKzOQcp12=s=puY7VFw@mail.gmail.com/ Signed-off-by: Jiaming Zhang Link: https://patch.msgid.link/20260625134933.425785-1-r772577952@gmail.com Signed-off-by: Takashi Iwai --- diff --git a/sound/usb/fcp.c b/sound/usb/fcp.c index ea746bdb36ffc..6f5dcd35e1d4a 100644 --- a/sound/usb/fcp.c +++ b/sound/usb/fcp.c @@ -1083,6 +1083,8 @@ static int fcp_find_fc_interface(struct usb_mixer_interface *mixer) if (desc->bInterfaceClass != 255) continue; + if (desc->bNumEndpoints < 1) + continue; epd = get_endpoint(intf->altsetting, 0); private->bInterfaceNumber = desc->bInterfaceNumber;