CVE-2026-63894 usb: gadget: f_fs: serialize DMABUF cancel against request completion

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: ffs: serialize DMABUF cancel against request completion ffsepfiledmabufiocomplete calls usbepfreerequest on the completed request but leaves priv-req, the back-pointer that ffsdmabuftransfer set on submission, pointi...