CVE-2026-98240

In the Linux kernel, the following vulnerability has been resolved:

net: ip tunnel: initialize options len before referencing options

The following command triggers a kernel panic:

ip link add d0 type dummy; ip link set d0 up ip route add 10.30.0.0/16 encap ip id 300 geneve opts 4660:66:11223344 dev d0

memcpy: detected buffer overflow: 4 byte write of buffer size 0 kernel BUG at lib/string helpers.c:1044! ... ip tun parse opts.part.0.cold+0x10/0x10 ip tun build state+0x116/0x2a0

On kernels built with GCC 15+ and CONFIG FORTIFY SOURCE, the fortified memcpy() got 0 sized destination with request of 4 bytes length:

static int ip tun parse opts geneve(...) { ... attr = tb[LWTUNNEL IP OPT GENEVE DATA]; data len = nla len(attr); /* == 4 */

struct geneve opt opt = ip tunnel info opts(info) + opts len; memcpy(opt->opt data, nla data(attr), data len); / ^^^^^^^^^^^^^ 0 since options len is assigned afterwards */

Fixed by initializing the counter before the options are referenced. Matching what tunnel key opts set() already does.