linux-kernel - Re: [patch] rapidio: use after free in unregister function

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Message-ID: <51D67066.9070105@gmail.com>
Date:	Fri, 05 Jul 2013 17:06:14 +1000
From:	Ryan Mallon <rmallon@...il.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
CC:	Matt Porter <mporter@...nel.crashing.org>,
	Alexandre Bounine <alexandre.bounine@....com>,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [patch] rapidio: use after free in unregister function

On 05/07/13 16:02, Dan Carpenter wrote:
> We need to use the _safe version of list_for_each_entry() because we
> are freeing the iterator.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> 
> diff --git a/drivers/rapidio/rio.c b/drivers/rapidio/rio.c
> index f4f30af..84ac64a 100644
> --- a/drivers/rapidio/rio.c
> +++ b/drivers/rapidio/rio.c
> @@ -1701,7 +1701,7 @@ EXPORT_SYMBOL_GPL(rio_register_scan);
>  int rio_unregister_scan(int mport_id, struct rio_scan *scan_ops)
>  {
>  	struct rio_mport *port;
> -	struct rio_scan_node *scan;
> +	struct rio_scan_node *scan, *tmp;
>  
>  	pr_debug("RIO: %s for mport_id=%d\n", __func__, mport_id);
>  
> @@ -1715,7 +1715,7 @@ int rio_unregister_scan(int mport_id, struct rio_scan *scan_ops)
>  		    (mport_id == RIO_MPORT_ANY && port->nscan == scan_ops))
>  			port->nscan = NULL;
>  
> -	list_for_each_entry(scan, &rio_scans, node)
> +	list_for_each_entry_safe(scan, tmp, &rio_scans, node)
>  		if (scan->mport_id == mport_id) {
>  			list_del(&scan->node);
>  			kfree(scan);

It looks like an mport_id can only be assigned to one scan entry (see
rio_register_scan), so you can use list_for_each_entry and break; after
the kfree(scan); instead.

~Ryan

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