linux-kernel - Re: [PATCH] usb: gadget: gadgetfs: correct dev state

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Date:	Thu, 05 Jun 2014 18:18:11 +0400
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Marcus Nutzinger <marcus.nutzinger@...obroma-systems.com>,
	Felipe Balbi <balbi@...com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: gadget: gadgetfs: correct dev state

Hello.

On 06/05/2014 05:08 PM, Marcus Nutzinger wrote:

> Commit 1826e9b1 fixes the use after free of "dev".

    Please also specify that commit's summary line in parens.

> However if this is not the final call to dev_release()
> and the state is not reset to STATE_DEV_DISABLED and
> hence all further open() calls to the gadgetfs ep0
> device will fail with EBUSY.

> So this commit reverts 1826e9b1 and places the call
> put_dev() after setting the state.

> Signed-off-by: Marcus Nutzinger <marcus.nutzinger@...obroma-systems.com>
> Reviewed-by: Christoph Muellner <christoph.muellner@...obroma-systems.com>
> ---
>   drivers/usb/gadget/inode.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)

> diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
> index a925d0c..6330528 100644
> --- a/drivers/usb/gadget/inode.c
> +++ b/drivers/usb/gadget/inode.c
> @@ -1264,8 +1264,13 @@ dev_release (struct inode *inode, struct file *fd)
>
>   	kfree (dev->buf);
>   	dev->buf = NULL;
> -	put_dev (dev);
>
> +	/* other endpoints were all decoupled from this device */
> +	spin_lock_irq(&dev->lock);
> +	dev->state = STATE_DEV_DISABLED;
> +	spin_unlock_irq(&dev->lock);

    Not sure I understand why you need spinlock here... isn't the assignment 
atomic already?

> +
> +	put_dev (dev);
>   	return 0;
>   }

WBR, Sergei

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