Re: [PATCH] nl80211: fix attrbuf access race by allocating a separate one

["John W. Linville" <linville-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>]

On Wed, Jun 19, 2013 at 01:39:00AM -0700, David Miller wrote:
> From: Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
> Date: Wed, 19 Jun 2013 10:23:58 +0200
> 
> > From: Johannes Berg <johannes.berg-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> > 
> > Since my commit 3713b4e364, nl80211_dump_wiphy() uses the global
> > nl80211_fam.attrbuf for parsing the incoming data. This wouldn't
> > be a problem if it only did so on the first dump iteration which
> > is locked against other commands in generic netlink, but due to
> > space constraints in cb->args (the needed state doesn't fit) I
> > decided to always parse the original message. That's racy though
> > since nl80211_fam.attrbuf could be used by some other parsing in
> > generic netlink concurrently.
> > 
> > For now, fix this by allocating a separate parse buffer (it's a
> > bit too big for the stack, currently 1448 bytes on 64-bit). For
> > -next, I'll change the code to parse into the global buffer in
> > the first round only and then allocate a smaller buffer to keep
> > the state in cb->args.
> > 
> > Reported-by: Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
> > Signed-off-by: Johannes Berg <johannes.berg-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> 
> Acked-by: David S. Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>

Acked-by: John W. Linville <linville-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>

-- 
John W. Linville		Someday the world will need a hero, and you
linville-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org			might be all we have.  Be ready.
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