---
id: CVE-2026-99166
title: 'net: rds: fix uninitialized trans dereference in CM event handler'
summary: |-
  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_NOD…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= dcdede0406d30e14a6ed727dce69dfac0518371d <
    5f23e4e3a31dacfd82a8f56be253adc0910ee84f
  - >-
    Linux >= dcdede0406d30e14a6ed727dce69dfac0518371d <
    ca14c289ed9ffed6cc64290d039e923e5720a8bf
  - >-
    Linux >= dcdede0406d30e14a6ed727dce69dfac0518371d <
    492ba6ac1b1ffb8a06ff52db0825c1af2cdb28c8
  - Linux 4.6
published: '2026-10-28'
updated: '2026-10-28'
sourceUpdated: '2026-10-28T10:35:18.050Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-99166'
references:
  - url: 'https://git.kernel.org/stable/c/5f23e4e3a31dacfd82a8f56be253adc0910ee84f'
  - url: 'https://git.kernel.org/stable/c/ca14c289ed9ffed6cc64290d039e923e5720a8bf'
  - url: 'https://git.kernel.org/stable/c/492ba6ac1b1ffb8a06ff52db0825c1af2cdb28c8'
tags:
  - cve.org
ingestedAt: '2026-10-28T11:09:40.390Z'
---

## Overview

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 request's
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 connection's 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

- `Linux >= dcdede0406d30e14a6ed727dce69dfac0518371d < 5f23e4e3a31dacfd82a8f56be253adc0910ee84f`
- `Linux >= dcdede0406d30e14a6ed727dce69dfac0518371d < ca14c289ed9ffed6cc64290d039e923e5720a8bf`
- `Linux >= dcdede0406d30e14a6ed727dce69dfac0518371d < 492ba6ac1b1ffb8a06ff52db0825c1af2cdb28c8`
- `Linux 4.6`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.