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

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Date:	Sat, 10 Nov 2007 21:34:33 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	kaber@...sh.net
Cc:	joe@...ches.com, mcgrof@...il.com, netdev@...r.kernel.org,
	linux-wireless@...r.kernel.org, jeff@...zik.org
Subject: Re: [PATCH] Fix infinite loop on dev_mc_unsync()

From: Patrick McHardy <kaber@...sh.net>
Date: Sat, 10 Nov 2007 01:13:42 +0100

> 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.

Agreed, this comment is pointless.

I'll apply Joe's patch without the comment.
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