---
id: CVE-2026-89532
title: 'svcrdma: Fix pcl_for_each_segment for empty chunks'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  svcrdma: Fix pcl_for_each_segment for empty chunks

  When a parsed chunk list contains a chunk whose ch_segcount is zero,
  pcl_for_each_segment computes its inclusive upp…
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-125
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 <
    1e2e3481e39103a386b86be1c33eaef97cbdf16e
  - >-
    Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 <
    3a78b841879c2a3243f74edc514236fb2907167f
  - >-
    Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 <
    06d0390c37fa6714624af771bd72bbf1a7ed9bb1
  - >-
    Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 <
    9c5a03c3dc505c0295339b0a1b9e4fe36447e482
  - >-
    Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 <
    a1c954ca4977a4e6ec73ef92fe48073ec54f9fc8
  - >-
    Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 <
    6d33a7e6bf6c6b293a266a617201285a1ad32c56
  - >-
    Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 <
    b7713a784c59515d0aba558c8f5df6a0164dd3a9
  - Linux 5.11
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-16T19:23:11.362883Z'
published: '2026-09-11'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:48:23.895Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89532'
references:
  - url: 'https://git.kernel.org/stable/c/1e2e3481e39103a386b86be1c33eaef97cbdf16e'
  - url: 'https://git.kernel.org/stable/c/3a78b841879c2a3243f74edc514236fb2907167f'
  - url: 'https://git.kernel.org/stable/c/06d0390c37fa6714624af771bd72bbf1a7ed9bb1'
  - url: 'https://git.kernel.org/stable/c/9c5a03c3dc505c0295339b0a1b9e4fe36447e482'
  - url: 'https://git.kernel.org/stable/c/a1c954ca4977a4e6ec73ef92fe48073ec54f9fc8'
  - url: 'https://git.kernel.org/stable/c/6d33a7e6bf6c6b293a266a617201285a1ad32c56'
  - url: 'https://git.kernel.org/stable/c/b7713a784c59515d0aba558c8f5df6a0164dd3a9'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89532.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89532'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532488'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89532'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89532'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89532.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.00502
epssPercentile: 0.42785
scores:
  cna: 9.1
  vendor: 7
ingestedAt: '2026-09-14T15:23:07.452Z'
---

## Overview

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

svcrdma: Fix pcl_for_each_segment for empty chunks

When a parsed chunk list contains a chunk whose ch_segcount is zero,
pcl_for_each_segment computes its inclusive upper bound as
&chunk->ch_segments[ch_segcount - 1]. ch_segcount is u32, so the
subtraction wraps to 0xFFFFFFFF and the bound lands far past the
ch_segments flex array. The loop body then walks unrelated memory at
sizeof(struct svc_rdma_segment) stride until it faults.

A zero-segcount chunk is reachable from the wire:
xdr_check_write_chunk() only rejects segcount values greater than
rc_maxpages, and pcl_alloc_write() links a freshly allocated chunk
onto rc_write_pcl/rc_reply_pcl before its segment-fill loop runs,
so a Write or Reply chunk advertising zero segments leaves
ch_segcount == 0 on the list. When the transport has negotiated
Send-With-Invalidate, svc_rdma_get_inv_rkey() iterates all four
PCLs with pcl_for_each_segment and dereferences segment->rs_handle
on each iteration, turning the underflow into an out-of-bounds read
and a general protection fault.

    xdr_check_write_list / xdr_check_reply_chunk
      pcl_alloc_write()
        chunk = pcl_alloc_chunk(...)  /* ch_segcount = 0 */
        list_add_tail(&chunk->ch_list, &pcl->cl_chunks)
        /* fill loop iterates zero times for wire segcount 0 */

    svc_rdma_get_inv_rkey()
      pcl_for_each_chunk(rc_write_pcl)
        pcl_for_each_segment(segment, chunk)
          pos <= &ch_segments[0u - 1u]  /* 0xFFFFFFFF */
          segment->rs_handle            /* OOB read -> GPF */

Fix by switching the macro to a half-open upper bound that uses
ch_segcount directly. For ch_segcount == 0 the loop start equals the
loop end and the body is skipped; for ch_segcount > 0 the iteration
range is unchanged. All six existing call sites in
net/sunrpc/xprtrdma/svc_rdma_recvfrom.c and
net/sunrpc/xprtrdma/svc_rdma_rw.c remain correct under the new bound,
so no caller changes are needed.

## Affected

- `Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 < 1e2e3481e39103a386b86be1c33eaef97cbdf16e`
- `Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 < 3a78b841879c2a3243f74edc514236fb2907167f`
- `Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 < 06d0390c37fa6714624af771bd72bbf1a7ed9bb1`
- `Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 < 9c5a03c3dc505c0295339b0a1b9e4fe36447e482`
- `Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 < a1c954ca4977a4e6ec73ef92fe48073ec54f9fc8`
- `Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 < 6d33a7e6bf6c6b293a266a617201285a1ad32c56`
- `Linux >= 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 < b7713a784c59515d0aba558c8f5df6a0164dd3a9`
- `Linux 5.11`

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89532.json)