CVE-2026-98008net: macb: fix NULL pointer dereference on unbind with fixed-link

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/afa224cabc0132ca414b9141b1a919ca2d318cd0
• https://git.kernel.org/stable/c/054ad8e66025eb4778d840bef80c270646cebcd2
• https://git.kernel.org/stable/c/f737d999fcb8f276d77b01ea4c2016ee01dad19b
• https://git.kernel.org/stable/c/5710f6a74f63cbba0e15cd75917234916181c9d4
• https://git.kernel.org/stable/c/edb39c7666bb3924da761dfb417db85c1e5d8ad3
• https://git.kernel.org/stable/c/38b6be101006d3e7af972999f45d4f1e8250587a