netdev - Re: [patch net-next 27/34] nfp: bpf: Convert ndo_setup

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Date:   Tue, 17 Oct 2017 20:16:47 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     netdev@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [patch net-next 27/34] nfp: bpf: Convert ndo_setup_tc offloads
 to block callbacks

Tue, Oct 17, 2017 at 04:39:59PM CEST, jakub.kicinski@...ronome.com wrote:
>On Tue, 17 Oct 2017 14:48:12 +0200, Jiri Pirko wrote:
>> Fri, Oct 13, 2017 at 03:08:24AM CEST, jakub.kicinski@...ronome.com wrote:
>> >On Thu, 12 Oct 2017 19:18:16 +0200, Jiri Pirko wrote:  
>> >> diff --git a/drivers/net/ethernet/netronome/nfp/bpf/offload.c b/drivers/net/ethernet/netronome/nfp/bpf/offload.c
>> >> index a88bb5b..9e9af88 100644
>> >> --- a/drivers/net/ethernet/netronome/nfp/bpf/offload.c
>> >> +++ b/drivers/net/ethernet/netronome/nfp/bpf/offload.c
>> >> @@ -246,6 +246,10 @@ int nfp_net_bpf_offload(struct nfp_net *nn, struct tc_cls_bpf_offload *cls_bpf)
>> >>  	void *code;
>> >>  	int err;
>> >>  
>> >> +	if (cls_bpf->common.protocol != htons(ETH_P_ALL) ||
>> >> +	    cls_bpf->common.chain_index)
>> >> +		return -EOPNOTSUPP;
>> >> +
>> >>  	max_instr = nn_readw(nn, NFP_NET_CFG_BPF_MAX_LEN);
>> >>  
>> >>  	switch (cls_bpf->command) {  
>> >
>> >It is certainly very ugly but I send a fake struct tc_cls_bpf_offload
>> >here for XDP.  Refactoring this mess is pretty high on my priority list
>> >but one way or the other this function will be called from XDP so TC
>> >checks must stay in the TC handler... :(  
>> 
>> Okay. But currently, why is it a problem? You don't need the checks for
>> xdp path.
>> 
>
>static int
>nfp_bpf_xdp_offload(struct nfp_app *app, struct nfp_net *nn,
>		    struct bpf_prog *prog)
>{
>	struct tc_cls_bpf_offload cmd = {
>		.prog = prog,
>	};
>	int ret;
>
>	if (!nfp_net_ebpf_capable(nn))
>		return -EINVAL;
>
>	if (nn->dp.ctrl & NFP_NET_CFG_CTRL_BPF) {
>		if (!nn->dp.bpf_offload_xdp)
>			return prog ? -EBUSY : 0;
>		cmd.command = prog ? TC_CLSBPF_REPLACE : TC_CLSBPF_DESTROY;
>	} else {
>		if (!prog)
>			return 0;
>		cmd.command = TC_CLSBPF_ADD;
>	}
>
>	ret = nfp_net_bpf_offload(nn, &cmd);
>	/* Stop offload if replace not possible */
>	if (ret && cmd.command == TC_CLSBPF_REPLACE)
>		nfp_bpf_xdp_offload(app, nn, NULL);
>	nn->dp.bpf_offload_xdp = prog && !ret;
>	return ret;
>}
>
>The fake offload struct is at the top of this function.  Dereferencing
>cls_bpf->common in nfp_net_bpf_offload() will crash the kernel.  Or am
>I missing something?

We just have to init it. Should not be a problem. Will add it.