linux-kernel - Re: [PATCH v2] uio: Fix uio driver to refcount device

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Date:	Wed, 18 Mar 2015 17:07:56 +0000
From:	Brian Russell <brian.russell@...cade.com>
To:	"Hans J. Koch" <hjk@...sjkoch.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] uio: Fix uio driver to refcount device

Responding to myself ...

On 13/03/15 10:17, Brian Russell wrote:
> Protect uio driver from crashing if its owner is hot unplugged while there
> are open fds.
> 
> Signed-off-by: Brian Russell <brussell@...cade.com>
> ---
>  drivers/uio/uio.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> index 6276f13..70ce015 100644
> --- a/drivers/uio/uio.c
> +++ b/drivers/uio/uio.c
> @@ -434,9 +434,11 @@ static int uio_open(struct inode *inode, struct file *filep)
>  		goto out;
>  	}
>  
> +	get_device(idev);
> +

This is bogus, idev is uio_device *, not device *. Turns out this patch only masked the crash I was seeing, so please ignore. Updated version to follow ...

Thanks,

Brian

>  	if (!try_module_get(idev->owner)) {
>  		ret = -ENODEV;
> -		goto out;
> +		goto err_module_get;
>  	}
>  
>  	listener = kmalloc(sizeof(*listener), GFP_KERNEL);
> @@ -462,6 +464,9 @@ err_infoopen:
>  err_alloc_listener:
>  	module_put(idev->owner);
>  
> +err_module_get:
> +	put_device(idev);
> +
>  out:
>  	return ret;
>  }
> @@ -485,6 +490,7 @@ static int uio_release(struct inode *inode, struct file *filep)
>  
>  	module_put(idev->owner);
>  	kfree(listener);
> +	put_device(idev);
>  	return ret;
>  }
>  
> 
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