Subject: Re: [PATCH] dsa: Fix conversion from host device to mii bus

From: Alexander Duyck <[email-masked]>
Date: Fri, 17 Oct 2014 16:02:02 -0700

On 10/17/2014 12:30 PM, Guenter Roeck wrote:
> Commit b4d2394d01bc ("dsa: Replace mii_bus with a generic host device")
> replaces mii_bus with a generic host_dev, and introduces
> dsa_host_dev_to_mii_bus() to support conversion from host_dev to mii_bus.
> However, in some cases it uses to_mii_bus to perform that conversion.
> Since host_dev is not the phy bus device but typically a platform device,
> this fails and results in a crash with the affected drivers.
>
> BUG: unable to handle kernel NULL pointer dereference at           (null)
> IP: [<ffffffff81781d35>] __mutex_lock_slowpath+0x75/0x100
> PGD 406783067 PUD 406784067 PMD 0
> Oops: 0002 [#1] SMP
> ...
> Call Trace:
> [<ffffffff810a538b>] ? pick_next_task_fair+0x61b/0x880
> [<ffffffff81781de3>] mutex_lock+0x23/0x37
> [<ffffffff81533244>] mdiobus_read+0x34/0x60
> [<ffffffff8153b95a>] __mv88e6xxx_reg_read+0x8a/0xa0
> [<ffffffff8153b9bc>] mv88e6xxx_reg_read+0x4c/0xa0
>
> Fixes: b4d2394d01bc ("dsa: Replace mii_bus with a generic host device")
> Cc: Alexander Duyck <[email-masked]>
> Signed-off-by: Guenter Roeck <[email-masked]>
> ---

The fix looks good to me.

Acked-by: Alexander Duyck <[email-masked]>