linux-kernel - Re: [PATCH] devres: Freeing the drs after all release() are called

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Message-ID: <20131106085859.GB9487@kroah.com>
Date:	Wed, 6 Nov 2013 00:58:59 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Chuansheng Liu <chuansheng.liu@...el.com>
Cc:	dmitry.torokhov@...il.com, tj@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] devres: Freeing the drs after all release() are called

On Wed, Nov 06, 2013 at 02:40:18PM +0800, Chuansheng Liu wrote:
> 
> In release_nodes(), it will call dr->node.release() and kfree
> dr one by one.
> 
> But sometimes the previous dr maybe be used by next .release(),
> such as:
> [50314.855534]  [<c12b172f>] ? synchronize_irq+0x3f/0xb0
> [50314.861193]  [<c12b18e9>] __free_irq+0x149/0x200
> [50314.866367]  [<c12b19e3>] free_irq+0x43/0xa0
> [50314.871152]  [<c12b4864>] devm_irq_release+0x14/0x20
> [50314.876713]  [<c169e806>] release_nodes+0x136/0x1b0
> [50314.882178]  [<c169ee79>] devres_release_all+0x39/0x60
> [50314.887935]  [<c169b411>] __device_release_driver+0x71/0xd0
> 
> the free_irq() will sync the last irq handling, which maybe use
> freed dr, then it will cause memory corruption.
> 
> Here split the dr kfreeing actions after all dr->node.release().

But you aren't really solving any problems here, how is dr being used
after the release function is called?  Who is doing it in such a way
that this change would really fix anything?

thanks,

greg k-h
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