linux-kernel - Re: [patch] hiddev: fix incorrect hiddev freeing

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Date:	Mon, 9 Mar 2009 03:38:02 +0100
From:	Johannes Weiner <hannes@...xchg.org>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Oliver Neukum <oliver@...kum.name>, linux-kernel@...r.kernel.org,
	stable@...nel.org
Subject: Re: [patch] hiddev: fix incorrect hiddev freeing

On Mon, Mar 09, 2009 at 03:31:51AM +0100, Johannes Weiner wrote:
> When hiddev_open() fails for whatever reason, free the just allocated
> hiddev_list structure shared hiddev potentially still in use.
                       ^
                   instead of

Sorry, it's late (or early?)  Need a resend?

> The hiddev is freed in device disconnect/last close of the device file
> and must not be freed while there are possibly existing references to
> it.
> 
> This is probably responsible for these
> 
>   http://kerneloops.org/oops.php?number=221185
>   http://kerneloops.org/oops.php?number=220365
> 
> where a reader sleeps on the waitqueue, the device gets disconnected
> (exist -> 0) another user tries to open it, fails on the exist check
> and frees the hiddev from the table.  The finish_wait() in the reader
> will then dereference the hiddev to get to the waitqueue and oopses.
> 
> This was introduced by commit 079034073faf974973baa0256b029451f6e768ad
> "HID: hiddev cleanup -- handle all error conditions properly".
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> Cc: Oliver Neukum <oliver@...kum.name>
> ---
> 
> diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
> index 4940e4d..00ea1ed 100644
> --- a/drivers/hid/usbhid/hiddev.c
> +++ b/drivers/hid/usbhid/hiddev.c
> @@ -306,7 +306,7 @@ static int hiddev_open(struct inode *inode, struct file *file)
>  	return 0;
>  bail:
>  	file->private_data = NULL;
> -	kfree(list->hiddev);
> +	kfree(list);
>  	return res;
>  }
>  
> --
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