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

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Message-Id: <20130619.013900.786603036908799505.davem@davemloft.net>
Date:	Wed, 19 Jun 2013 01:39:00 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	johannes@...solutions.net
Cc:	torvalds@...ux-foundation.org, linville@...driver.com,
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] nl80211: fix attrbuf access race by allocating a
 separate one

From: Johannes Berg <johannes@...solutions.net>
Date: Wed, 19 Jun 2013 10:23:58 +0200

> From: Johannes Berg <johannes.berg@...el.com>
> 
> 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@...ux-foundation.org>
> Signed-off-by: Johannes Berg <johannes.berg@...el.com>

Acked-by: David S. Miller <davem@...emloft.net>
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