net/iucv: filter frames in afiucv_hs_rcv() by ingress device

Summary

In the Linux kernel, the following vulnerability has been resolved: net/iucv: filter frames in afiucv_hs_rcv() by ingress device afiucv_hs_rcv() selects a socket from iucv_sk_list by matching four 8-byte name fields in the transport header alone. No check is made against the net_device the frame arrived on. This can cause a frame arriving on any netdev to be delivered to an AF_IUCV socket. Three problems follow. First, a frame arriving over HiperSockets can be delivered to a socket bound to the classic z/VM IUCV transport, which has iucv->hs_dev == NULL. iucv_sock_bind() takes the classic path whenever the requested userid matches iucv_userid, even on a guest that also has a HiperSockets device carrying the same identifier. The child socket created by afiucv_hs_callback_syn() for such a match inherits hs_dev = NULL and transport = AF_IUCV_TRANS_HIPER, so the first send() on it returns -ENODEV. The socket delivered to accept() is unusable. Second, a frame arriving on one netdev can be delivered to a socket bound to a different IQD device. Which can lead to • Accept-queue exhaustion (DoS) • Attacker-controlled peer identity in the child socket • Data injection into existing sockets • Fabric noise on the IQD fabric, where bogus replies are sent • killing established connections Third, all AF_IUCV sockets live in init_net, as iucv_sock_alloc() calls sk_alloc(&init_net, ...). But even frames arriving on netdev devices in a namespace can be delivered to an IUCV socket. So a process in an unprivileged user and network namespace holding only the CAP_NET_RAW capability valid within that namespace can send a raw ETH_P_AF_IUCV frame on its own lo device and have it matched against init_net sockets. Fix all three by skipping any socket whose hs_dev does not match the ingress device. A classic z/VM IUCV socket has hs_dev == NULL; the ingress dev is never NULL, so classic sockets are skipped automatically. An unbound HIPER socket also has hs_dev == NULL and is skipped. A bound HIPER socket is only reachable from the exact IQD device it was bound to. Because hs_dev is always a device in init_net (iucv_sock_bind() scans for_each_netdev_rcu(&init_net, ...) exclusively), a frame whose ingress device belongs to another namespace never matches any socket. Note that AF_IUCV over HiperSockets provides no per-connection authentication: no sequence numbers, no TLS, no nonce. The four name fields identifying a connection are exchanged in plaintext on the shared HiperSockets segment (VCHID). Any host on the same HiperSockets segment could spoof any frame type against an existing connection. That is a protocol-level property unchanged by this patch. The fix reduces the attack surface to peers present on the same HiperSockets segment.

Timeline

1. Sep 11, 2026, 7:42 PM UTCCVE published
2. Oct 19, 2026, 8:46 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 3881ac441f642d56503818123446f7298442236b · fixed in 639828ad4d374056167391dbaffd13dd5e5e5ddb; From 3881ac441f642d56503818123446f7298442236b · fixed in 92e5c281f1caa287bb58292f2687c9e3ff3aa23e; From 3881ac441f642d56503818123446f7298442236b · fixed in 712330f8a4293cfd97b0d62b7c7dc01862a16b98; From 3881ac441f642d56503818123446f7298442236b · fixed in 0a5af67e7184c6a0e155c317840bd64b37177af4; From 3881ac441f642d56503818123446f7298442236b · fixed in dfac2936b83be00035ae176f8252e1c1e1de9207; From 3881ac441f642d56503818123446f7298442236b · fixed in 8e3763f1ccac3fc395f9af2b87114c023ced8a3f; From 3881ac441f642d56503818123446f7298442236b · fixed in a7f0130a091724e69827ab58e74777a88747e892; From 3881ac441f642d56503818123446f7298442236b · fixed in 80230a18c164a4b5bbc048fe2768b219ac17bc5a

• Linux Linux

  3.2

• KernelLinux

  From 3.2.0 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.109; From 6.13.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 8