Bug 2541229 (CVE-2026-98008)

Summary: CVE-2026-98008 kernel: net: macb: fix NULL pointer dereference on unbind with fixed-link
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Cadence MACB ethernet driver. A local user with administrative privileges could cause a denial of service (DoS) by triggering a driver unbind operation or an initialization failure on a device configured with a fixed-link connection. In this configuration, the driver fails to allocate an internal bus structure, causing cleanup routines to dereference a NULL pointer and crash the kernel.
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Description OSIDB Bzimport 2026-09-25 11:06:11 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net: macb: fix NULL pointer dereference on unbind with fixed-link

When the device tree describes a fixed-link and has no "mdio" child
node, macb_mii_init() returns early without allocating the MDIO bus,
leaving bp->mii_bus as NULL.

Two cleanup paths then dereference this NULL bus:

1. On driver unbind, macb_remove() unconditionally calls
   mdiobus_unregister(bp->mii_bus), which oopses:

  Unable to handle kernel NULL pointer dereference at virtual address 00000000000004a8
  pc : mdiobus_unregister+0x14/0xa4
  lr : macb_remove+0x38/0xa4
  Call trace:
   mdiobus_unregister+0x14/0xa4 (P)
   macb_remove+0x38/0xa4
   platform_remove+0x20/0x30
   device_release_driver_internal+0x1c8/0x224
   unbind_store+0xb4/0xbc

2. On the probe error path in macb_probe(), reached when
   macb_mii_init() has succeeded but a subsequent step fails, the
   err_out_unregister_mdio label runs the same unconditional cleanup.

mdiobus_unregister() and mdiobus_free() do not guard against a NULL
bus, so guard the calls in both macb_remove() and the probe error
path.
Comment 1 Keith Grant 2026-09-28 19:15:28 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98008.mbox