---
id: CVE-2026-72491
title: 'net/9p: fix race condition on rdma->state in trans_rdma.c'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/9p: fix race condition on rdma->state in trans_rdma.c

  The rdma->state field is modified without holding req_lock in both
  recv_done() and p9_cm_event_handler(), whi…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b <
    4cee2b8766045059d5e0b8114837b4a8efe827ac
  - >-
    Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b <
    5424138848eb7d7d8a7196676e90a2cbf2142454
  - >-
    Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b <
    3970a19a80de530b801b6256354d4a529a9a2d6c
  - >-
    Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b <
    8aadc136d8e8d8fc95d7982d213cfe2234dfcf2b
  - >-
    Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b <
    151f8cf5b23d8a534d884432a82a6d54d5a61989
  - >-
    Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b <
    13bf9879b778b2f4b260b45bed18f31806120d1e
  - >-
    Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b <
    ebbcbe5c0db215feecc17def06178da443f4eea6
  - >-
    Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b <
    7d54894a1ee265a72d70f7cae1da6cc774cccc71
  - Linux 3479b3c35e82ed10aa0ca2ee9e78c4eded06ba62
  - Linux c01ddaa54d7411e964ffd250c018d8469c5852f2
  - Linux 9e69c673fe077b8dc491cd8406c9bdcb1f76dee2
  - Linux e48e7e27e4dfd00c81e0381e7cee610cce021452
  - Linux >= 4.4.185 < 4.5
  - Linux >= 4.9.185 < 4.10
  - Linux >= 4.14.132 < 4.15
  - Linux >= 4.19.57 < 4.20
  - Linux 4.20
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-10-16T18:50:50.731501Z'
published: '2026-08-15'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T18:55:26.515Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-72491'
references:
  - url: 'https://git.kernel.org/stable/c/4cee2b8766045059d5e0b8114837b4a8efe827ac'
  - url: 'https://git.kernel.org/stable/c/5424138848eb7d7d8a7196676e90a2cbf2142454'
  - url: 'https://git.kernel.org/stable/c/3970a19a80de530b801b6256354d4a529a9a2d6c'
  - url: 'https://git.kernel.org/stable/c/8aadc136d8e8d8fc95d7982d213cfe2234dfcf2b'
  - url: 'https://git.kernel.org/stable/c/151f8cf5b23d8a534d884432a82a6d54d5a61989'
  - url: 'https://git.kernel.org/stable/c/13bf9879b778b2f4b260b45bed18f31806120d1e'
  - url: 'https://git.kernel.org/stable/c/ebbcbe5c0db215feecc17def06178da443f4eea6'
  - url: 'https://git.kernel.org/stable/c/7d54894a1ee265a72d70f7cae1da6cc774cccc71'
tags:
  - cve.org
epss: 0.00734
epssPercentile: 0.53476
ingestedAt: '2026-10-16T19:46:24.391Z'
---

## Overview

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

net/9p: fix race condition on rdma->state in trans_rdma.c

The rdma->state field is modified without holding req_lock in both
recv_done() and p9_cm_event_handler(), while rdma_request() accesses
the same field under the req_lock spinlock. This inconsistent locking
creates a race condition:

- recv_done() running in softirq completion context sets
  rdma->state = P9_RDMA_FLUSHING without acquiring req_lock

- p9_cm_event_handler() modifies rdma->state at multiple points
  (ADDR_RESOLVED, ROUTE_RESOLVED, ESTABLISHED, CLOSED) without
  req_lock

- rdma_request() uses spin_lock_irqsave(&rdma->req_lock, flags) to
  protect the read-modify-write of rdma->state

The race can cause lost state transitions: recv_done() or the CM
event handler could set state to FLUSHING/CLOSED while rdma_request()
is concurrently checking or modifying state under the lock, leading to
the FLUSHING transition being silently overwritten by CLOSING. This
corrupts the connection state machine and can cause use-after-free on
RDMA request objects during teardown.

Fix by adding req_lock protection to all rdma->state modifications in
recv_done() and p9_cm_event_handler(), matching the pattern already
used in rdma_request(). Use spin_lock_irqsave/spin_unlock_irqrestore
in the CM event handler since it can race with recv_done() which runs
in softirq context.

Tested with a kernel module that races two threads (simulating
rdma_request and recv_done/CM handler) on rdma->state with proper
locking: 5.5M+ FLUSHING writes over 27M iterations with 0 lost
transitions.

## Affected

- `Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b < 4cee2b8766045059d5e0b8114837b4a8efe827ac`
- `Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b < 5424138848eb7d7d8a7196676e90a2cbf2142454`
- `Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b < 3970a19a80de530b801b6256354d4a529a9a2d6c`
- `Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b < 8aadc136d8e8d8fc95d7982d213cfe2234dfcf2b`
- `Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b < 151f8cf5b23d8a534d884432a82a6d54d5a61989`
- `Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b < 13bf9879b778b2f4b260b45bed18f31806120d1e`
- `Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b < ebbcbe5c0db215feecc17def06178da443f4eea6`
- `Linux >= 473c7dd1d7b59ff8f88a5154737e3eac78a96e5b < 7d54894a1ee265a72d70f7cae1da6cc774cccc71`
- `Linux 3479b3c35e82ed10aa0ca2ee9e78c4eded06ba62`
- `Linux c01ddaa54d7411e964ffd250c018d8469c5852f2`
- `Linux 9e69c673fe077b8dc491cd8406c9bdcb1f76dee2`
- `Linux e48e7e27e4dfd00c81e0381e7cee610cce021452`
- `Linux >= 4.4.185 < 4.5`
- `Linux >= 4.9.185 < 4.10`
- `Linux >= 4.14.132 < 4.15`
- `Linux >= 4.19.57 < 4.20`
- `Linux 4.20`

## Remediation

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