In the Linux kernel, the following vulnerability has been resolved:
bpf, xdp: move offload check into dev_xdp_install()
bpf_xdp_link_update() calls dev_xdp_install() directly and skips
dev_xdp_attach(), so the checks in dev_xdp_attach() do not run. A user can
make an XDP link with a normal program and then swap in an offloaded or
device-bound program with BPF_LINK_UPDATE, which puts it on the software
path.
dev_xdp_install() is the one place all three paths go through:
“ip link set xdp” and BPF_LINK_CREATE reach it via dev_xdp_attach(), and
BPF_LINK_UPDATE calls it directly. So move the program checks (offloaded,
bound to another device, device-bound in generic mode, native vs generic,
DEVMAP and CPUMAP) there, and keep only the netlink-flag check
(XDP_FLAGS_UPDATE_IF_NOEXIST) in dev_xdp_attach().
