netdev - Re: [Security] [PATCH] Integer overflow in RDS cmsg handling

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Message-ID: <AANLkTi=K4X3oK2oNVQiysL3FwSv0HtViPfkrgpY4t9YD@mail.gmail.com>
Date:	Wed, 17 Nov 2010 12:07:17 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	David Miller <davem@...emloft.net>
Cc:	drosenberg@...curity.com, andy.grover@...cle.com,
	netdev@...r.kernel.org, security@...nel.org
Subject: Re: [Security] [PATCH] Integer overflow in RDS cmsg handling

On Wed, Nov 17, 2010 at 9:52 AM, David Miller <davem@...emloft.net> wrote:
>
> Applied, thanks Dan.

Why is the cast there? It looks really odd. And it's definitely
pointless, since nr_local is already "uint64_t".

If the issue is that people don't want to worry about the signedness
of nr_local (which isn't obvious in the local scope), then I think it
would be _much_ better to write the code as

  if (args->nr_local < 0 || args->nr_local >UIO_MAXIOV)

than to have an illogical cast in there. Maybe we should add a helper
function ("in_range()" or whatever) that does this.

IOW, maybe something like

   if (!in_range(args->nr_local, 0, UID_MAXIOV))

would be nicer? With some appropriate macro magic to make it all type-safe?

                   Linus
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