netdev - Re: [PATCH] Fix infinite loop on dev_mc

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Date:	Sat, 10 Nov 2007 01:13:42 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Joe Perches <joe@...ches.com>
CC:	"Luis R. Rodriguez" <mcgrof@...il.com>, netdev@...r.kernel.org,
	linux-wireless@...r.kernel.org, Jeff Garzik <jeff@...zik.org>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH] Fix infinite loop on dev_mc_unsync()

Joe Perches wrote:
> On Sat, 2007-11-10 at 00:12 +0100, Patrick McHardy wrote:
>   
>> This may cause a use-after-free since __dev_addr_delete frees the address
>> when all references are gone.
>>     
>
> How about a comment then?  Perhaps:
>
> diff --git a/net/core/dev_mcast.c b/net/core/dev_mcast.c
> index ae35405..63576aa 100644
> --- a/net/core/dev_mcast.c
> +++ b/net/core/dev_mcast.c
> @@ -165,16 +165,23 @@ void dev_mc_unsync(struct net_device *to, struct net_device *from)
>  	netif_tx_lock_bh(from);
>  	netif_tx_lock_bh(to);
>  
> +	/*
> +	  This while loop can't be written as
> +		for (da = from->mc_list; da; da = da->next)
> +	  da = from->mc_list and __dev_addr_delete can kfree(from->mc_list)
> +	  which could cause a use-after-free of da->next
> +	*/
>   

Seems unnecessary to me, we also don't comment each list_for_each_entry_safe
iteration. I consider the use of a seperate next variable self-explanatory.


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