---
id: CVE-2026-23438
title: 'net: mvpp2: guard flow control update with global_tx_fc in buffer switching'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: mvpp2: guard flow control update with global_tx_fc in buffer switching

  mvpp2_bm_switch_buffers() unconditionally calls
  mvpp2_bm_pool_update_priv_fc() when switchi…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a <
    0cfcd31f98fc608dc9406bff3fee3a9dd364d014
  - >-
    Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a <
    da089f74a993f846685067b14158cb41b879ff29
  - >-
    Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a <
    ff0c54f088f7ab91dbbf47cf8244460f99122750
  - >-
    Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a <
    7bd20f4b3ef3044dc55acd5b8ef748a70d29d03f
  - >-
    Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a <
    7df2b50cae1a76cbb90b294f3edb61e3e10bf2e9
  - >-
    Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a <
    8baced53a35fc9710f80d6ca016a2c418dc3231f
  - >-
    Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a <
    8a63baadf08453f66eb582fdb6dd234f72024723
  - Linux 5.12
published: '2026-04-03'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T08:46:11.063Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-23438'
references:
  - url: 'https://git.kernel.org/stable/c/0cfcd31f98fc608dc9406bff3fee3a9dd364d014'
  - url: 'https://git.kernel.org/stable/c/da089f74a993f846685067b14158cb41b879ff29'
  - url: 'https://git.kernel.org/stable/c/ff0c54f088f7ab91dbbf47cf8244460f99122750'
  - url: 'https://git.kernel.org/stable/c/7bd20f4b3ef3044dc55acd5b8ef748a70d29d03f'
  - url: 'https://git.kernel.org/stable/c/7df2b50cae1a76cbb90b294f3edb61e3e10bf2e9'
  - url: 'https://git.kernel.org/stable/c/8baced53a35fc9710f80d6ca016a2c418dc3231f'
  - url: 'https://git.kernel.org/stable/c/8a63baadf08453f66eb582fdb6dd234f72024723'
tags:
  - cve.org
epss: 0.00125
epssPercentile: 0.01902
ingestedAt: '2026-09-08T15:33:26.992Z'
---

## Overview

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

net: mvpp2: guard flow control update with global_tx_fc in buffer switching

mvpp2_bm_switch_buffers() unconditionally calls
mvpp2_bm_pool_update_priv_fc() when switching between per-cpu and
shared buffer pool modes. This function programs CM3 flow control
registers via mvpp2_cm3_read()/mvpp2_cm3_write(), which dereference
priv->cm3_base without any NULL check.

When the CM3 SRAM resource is not present in the device tree (the
third reg entry added by commit 60523583b07c ("dts: marvell: add CM3
SRAM memory to cp11x ethernet device tree")), priv->cm3_base remains
NULL and priv->global_tx_fc is false. Any operation that triggers
mvpp2_bm_switch_buffers(), for example an MTU change that crosses
the jumbo frame threshold, will crash:

  Unable to handle kernel NULL pointer dereference at
  virtual address 0000000000000000
  Mem abort info:
    ESR = 0x0000000096000006
    EC = 0x25: DABT (current EL), IL = 32 bits
  pc : readl+0x0/0x18
  lr : mvpp2_cm3_read.isra.0+0x14/0x20
  Call trace:
   readl+0x0/0x18
   mvpp2_bm_pool_update_fc+0x40/0x12c
   mvpp2_bm_pool_update_priv_fc+0x94/0xd8
   mvpp2_bm_switch_buffers.isra.0+0x80/0x1c0
   mvpp2_change_mtu+0x140/0x380
   __dev_set_mtu+0x1c/0x38
   dev_set_mtu_ext+0x78/0x118
   dev_set_mtu+0x48/0xa8
   dev_ifsioc+0x21c/0x43c
   dev_ioctl+0x2d8/0x42c
   sock_ioctl+0x314/0x378

Every other flow control call site in the driver already guards
hardware access with either priv->global_tx_fc or port->tx_fc.
mvpp2_bm_switch_buffers() is the only place that omits this check.

Add the missing priv->global_tx_fc guard to both the disable and
re-enable calls in mvpp2_bm_switch_buffers(), consistent with the
rest of the driver.

## Affected

- `Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a < 0cfcd31f98fc608dc9406bff3fee3a9dd364d014`
- `Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a < da089f74a993f846685067b14158cb41b879ff29`
- `Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a < ff0c54f088f7ab91dbbf47cf8244460f99122750`
- `Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a < 7bd20f4b3ef3044dc55acd5b8ef748a70d29d03f`
- `Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a < 7df2b50cae1a76cbb90b294f3edb61e3e10bf2e9`
- `Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a < 8baced53a35fc9710f80d6ca016a2c418dc3231f`
- `Linux >= 3a616b92a9d17448d96a33bf58e69f01457fd43a < 8a63baadf08453f66eb582fdb6dd234f72024723`
- `Linux 5.12`

## Remediation

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