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ALSA: FCP: Fix NULL pointer dereference in interface lookup

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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: 46757a3e7d ("ALSA: FCP: Add Focusrite Control Protocol driver")
Reported-by: Jiaming Zhang <r772577952@gmail.com>
Closes: https://lore.kernel.org/lkml/CANypQFb1EHj0xX8bA1WxSOSK-5xca6ZNKzOQcp12=s=puY7VFw@mail.gmail.com/
Signed-off-by: Jiaming Zhang <r772577952@gmail.com>
Link: https://patch.msgid.link/20260625134933.425785-1-r772577952@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Jiaming Zhang
2026-06-25 21:49:33 +08:00
committed by Takashi Iwai
parent 9dbbe81962
commit e1e31e0ec8
1 changed files with 2 additions and 0 deletions
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2
sound/usb/fcp.c
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@@ -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;