CVE-2026-99166

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

net: rds: fix uninitialized trans dereference in CM event handler

rds_rdma_cm_event_handler_cmn() assigns trans only when the RDMA device is an InfiniBand CA (RDMA_NODE_IB_CA). On any other device type, e.g. an iWARP RNIC such as siw, trans stays uninitialized, but the event switch dereferences it: unconditionally in the RDMA_CM_EVENT_CONNECT_REQUEST case via trans->cm_handle_connect(), and (with a connection context) in the ROUTE_RESOLVED and ESTABLISHED cases.

An RDS listener on an iWARP device therefore crashes the kernel as soon as a connect request arrives: with CONFIG_INIT_STACK_ALL_ZERO the wild load becomes a NULL dereference at offset 0xa0 (&trans->cm_handle_connect) in the iw_cm_wq workqueue.

GCC masks the bug in default builds by folding the uninitialized load into &rds_ib_transport; Clang-built kernels take the real uninitialized path and oops.

The active side can land on a non-IB device too: the id that rds_ib_conn_path_connect() creates is not restricted to a node type, so rdma_resolve_addr() binds it to whichever device serves the local address, and an iWARP RNIC on the same netdev qualifies. The crash there is different: resolving a route on an iWARP id never fills in cm_id->route.path_rec, and the ROUTE_RESOLVED case writes path_rec[0].sl before it calls into the transport.

The iWARP transport was dropped long ago and IB is the only transport left, so make that explicit: initialize trans to &rds_ib_transport at declaration, drop the conditional assignment, reject a connect request that arrives on a non-IB device, and drop a connection whose address resolved to one instead of resolving a route on it. The rejection is limited to RDMA_CM_EVENT_CONNECT_REQUEST on purpose: a non-zero return from the handler makes rdma_cm destroy the id the event was delivered on, which is right for the requests freshly created id but would free a connection id that RDS still owns for any other event. On the active side the id stays ic->i_cm_id and the connections shutdown destroys it, so that case returns 0.

[achender: reject only on RDMA_CM_EVENT_CONNECT_REQUEST instead of bailing out for every event on a non-IB device, so that rdma_cm does not destroy connection ids RDS still tracks; drop a connection whose address resolved to a non-IB device before a route is resolved on it; changelog adjusted]

Affected Software

References

• https://git.kernel.org/stable/c/074bb7cdc3e26afa698888ba56fc1df0e3f24650
• https://git.kernel.org/stable/c/0d15e853aa88da5375edd32b39d08a048b64a1c5
• https://git.kernel.org/stable/c/492ba6ac1b1ffb8a06ff52db0825c1af2cdb28c8
• https://git.kernel.org/stable/c/5f23e4e3a31dacfd82a8f56be253adc0910ee84f
• https://git.kernel.org/stable/c/8973f70cb068012d83cff1cfa3f45ef94ab02267
• https://git.kernel.org/stable/c/8c77774535c3d6162929521a6fa11e3db086fa32
• https://git.kernel.org/stable/c/a2fde862b98db8908e2ebaffbb35a75a0e9d5b33
• https://git.kernel.org/stable/c/ca14c289ed9ffed6cc64290d039e923e5720a8bf