From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: David Laight <David.Laight@aculab.com>
Cc: Christoph Hellwig <hch@lst.de>,
"David S. Miller" <davem@davemloft.net>,
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Kernel Hardening <kernel-hardening@lists.openwall.com>
Subject: Re: [PATCH 12/26] netfilter: switch nf_setsockopt to sockptr_t
Date: Tue, 28 Jul 2020 10:17:28 +0200 [thread overview]
Message-ID: <CAHmME9pUbRmJq1Qcj10eENt15cuQHkiXJNKrUDmmC18n2mLKDA@mail.gmail.com> (raw)
In-Reply-To: <908ed73081cc42d58a5b01e0c97dbe47@AcuMS.aculab.com>
On Tue, Jul 28, 2020 at 10:07 AM David Laight <David.Laight@aculab.com> wrote:
>
> From: Christoph Hellwig
> > Sent: 27 July 2020 17:24
> >
> > On Mon, Jul 27, 2020 at 06:16:32PM +0200, Jason A. Donenfeld wrote:
> > > Maybe sockptr_advance should have some safety checks and sometimes
> > > return -EFAULT? Or you should always use the implementation where
> > > being a kernel address is an explicit bit of sockptr_t, rather than
> > > being implicit?
> >
> > I already have a patch to use access_ok to check the whole range in
> > init_user_sockptr.
>
> That doesn't make (much) difference to the code paths that ignore
> the user-supplied length.
> OTOH doing the user/kernel check on the base address (not an
> incremented one) means that the correct copy function is always
> selected.
Right, I had the same reaction in reading this, but actually, his code
gets rid of the sockptr_advance stuff entirely and never mutates, so
even though my point about attacking those pointers was missed, the
code does the better thing now -- checking the base address and never
mutating the pointer. So I think we're good.
>
> Perhaps the functions should all be passed a 'const sockptr_t'.
> The typedef could be made 'const' - requiring non-const items
> explicitly use the union/struct itself.
I was thinking the same, but just by making the pointers inside the
struct const. However, making the whole struct const via the typedef
is a much better idea. That'd probably require changing the signature
of init_user_sockptr a bit, which would be fine, but indeed I think
this would be a very positive change.
Jason
prev parent reply other threads:[~2020-07-28 8:18 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200723060908.50081-1-hch@lst.de>
[not found] ` <20200723060908.50081-13-hch@lst.de>
[not found] ` <20200727150310.GA1632472@zx2c4.com>
[not found] ` <20200727150601.GA3447@lst.de>
2020-07-27 16:16 ` [PATCH 12/26] netfilter: switch nf_setsockopt to sockptr_t Jason A. Donenfeld
2020-07-27 16:23 ` Christoph Hellwig
2020-07-28 8:07 ` David Laight
2020-07-28 8:17 ` Jason A. Donenfeld [this message]
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