Re: [PATCH net] net: macb: fix NULL pointer dereference on unbind with fixed-link

[Xuanqiang Luo <xuanqiang.luo@linux.dev>]

在 2026/9/2 18:28, Vineeth Karumanchi 写道:
> 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.
>
> Fixes: d0c3601f2c4e ("net: macb: Avoid 20s boot delay by skipping MDIO bus registration for fixed-link PHY")
> Signed-off-by: Vineeth Karumanchi <vineeth.karumanchi@amd.com>

Reviewed-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>

Thanks,
Xuanqiang