Re: [PATCH -next,v4] serial: core: fix NULL/dangling port_dev on failed re-register

[sashiko-bot@kernel.org]

> From: Cui GaoSheng <cuigaosheng1@huawei.com>
> 
> serial8250_unregister_port() removes a port and then re-registers it
> against the legacy serial8250 device when that device is still
> present, ignoring the return value of uart_add_one_port(). When the
> re-register fails, the error path of serial_core_register_port()
> removes the port device but leaves port->port_dev dangling (or NULL
> if the port device allocation itself failed). serial8250 matches
> ports on ->dev, so such half-registered slots still reach
> serial_core_unregister_port() on the next unbind:
> 
>   KASAN: null-ptr-deref in range [0x40-0x47]
>   RIP: serial_core_unregister_port+0xe5/0xa00
>     serial8250_unregister_port+0x103
>     serial8250_remove+0x61
> 
> Fix the error path to clear port->port_dev, and bail out of
> serial_core_unregister_port() when port_dev is NULL. Read
> port->port_dev under port_mutex, like all of its writers.
> 
> Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM")
> Assisted-by: LLM
> Signed-off-by: Cui GaoSheng <cuigaosheng1@huawei.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260929023155.3259567-1-cuigaosheng1@huawei.com?part=1