linux-kernel - Re: [PATCH] usb: ulpi: don't register drivers if bus doesn't exist

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Date:	Sun, 24 May 2015 00:19:48 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	heikki.krogerus@...ux.intel.com, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, david.a.cohen@...ux.intel.com,
	balbi@...com
Subject: Re: [PATCH] usb: ulpi: don't register drivers if bus doesn't exist

On Wed, May 20, 2015 at 03:33:26PM -0400, Sasha Levin wrote:
> ULPI registers it's bus at module_init so if the bus fails to register, the
> module will fail to load and all will be well in the world.
> 
> However, if the ULPI code is built-in rather than a module, the bus
> initialization may fail but we'd still try to register drivers later onto
> a non-existant bus, which will panic the kernel.
> 
> Fix that by checking that the bus was indeed initialized before trying to
> register drivers on top of it.
> 
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> ---
>  drivers/usb/common/ulpi.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
> index 0e6f968..0b0a5e7 100644
> --- a/drivers/usb/common/ulpi.c
> +++ b/drivers/usb/common/ulpi.c
> @@ -132,6 +132,10 @@ int ulpi_register_driver(struct ulpi_driver *drv)
>  	if (!drv->probe)
>  		return -EINVAL;
>  
> +	/* Was the bus registered successfully? */
> +	if (!ulpi_bus.p)
> +		return -ENODEV;

Ick, no, don't go mucking around in the bus internals like this, that's
not ok.  You should either "know" the bus is registered, or something is
really wrong with the design here.

greg k-h
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