linux-kernel - Re: [PATCH net-next] net: filter: rename 'struct sk_filter' to 'struct bpf

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Date:	Fri, 25 Jul 2014 13:54:37 +0200
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	Daniel Borkmann <dborkman@...hat.com>
Cc:	Alexei Starovoitov <ast@...mgrid.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, willemb@...gle.com,
	netfilter-devel@...r.kernel.org
Subject: Re: [PATCH net-next] net: filter: rename 'struct sk_filter' to
 'struct bpf_prog'

On Fri, Jul 25, 2014 at 01:25:35PM +0200, Daniel Borkmann wrote:
> [ also Cc'ing Willem, Pablo ]
> 
> On 07/25/2014 10:04 AM, Alexei Starovoitov wrote:
> >'sk_filter' name is used as 'struct sk_filter', function sk_filter() and
> >as variable 'sk_filter', which makes code hard to read.
> >Also it's easily confused with 'struct sock_filter'
> >Rename 'struct sk_filter' to 'struct bpf_prog' to clarify semantics and
> >align the name with generic BPF use model.
> 
> Agreed, as we went for kernel/bpf/, renaming makes absolutely sense.

My nft socket filtering changes are accomodated into struct sk_filter,
and will still be, so I still need some generic name there...

Please, leave this as it is.

> >The only ugly place is uapi/linux/netfilter/xt_bpf.h which
> >managed to expose kernel internal structure into uapi header.
> >Though it shouldn't even compile in user space, preserve the mess by
> >adding empty 'struct sk_filter;' there and type cast it to 'struct bpf_prog'
> >inside kernel in net/netfilter/xt_bpf.c
> >
> >Signed-off-by: Alexei Starovoitov <ast@...mgrid.com>
> >---
> >
> >alternative fix for xt_bpf.h could be to replace:
> >         /* only used in the kernel */
> >	struct sk_filter *filter __attribute__((aligned(8)));
> >with
> >         /* only used in the kernel */
> >	void *filter __attribute__((aligned(8)));
> >
> >but this 'void *' approach may further break broken userspace,
> >whereas the fix implemented here is more seamless.
> 
> Yep, that's not good, 'struct sk_filter' should never have been in a uapi
> file actually.

You can just send me a patch to change it to void. It's an internal
kernel pointer as the comment states. There is **no** way that
userspace can lurk with that from iptables at all.
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