Re: [PATCH net-next 1/2] bpf: skip sockopt hooks without CONFIG_NET

[Yonghong Song]

On 7/8/19 5:57 AM, Arnd Bergmann wrote:
> When CONFIG_NET is disabled, we get a link error:
> 
> kernel/bpf/cgroup.o: In function `__cgroup_bpf_run_filter_setsockopt':
> cgroup.c:(.text+0x3010): undefined reference to `lock_sock_nested'
> cgroup.c:(.text+0x3258): undefined reference to `release_sock'
> kernel/bpf/cgroup.o: In function `__cgroup_bpf_run_filter_getsockopt':
> cgroup.c:(.text+0x3568): undefined reference to `lock_sock_nested'
> cgroup.c:(.text+0x3870): undefined reference to `release_sock'
> kernel/bpf/cgroup.o: In function `cg_sockopt_func_proto':
> cgroup.c:(.text+0x41d8): undefined reference to `bpf_sk_storage_delete_proto'
> 
> None of this code is useful in this configuration anyway, so we can
> simply hide it in an appropriate #ifdef.
> 
> Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>

FYI.

There is already a patch to fix the same issue,
https://lore.kernel.org/bpf/e9e489fe-feec-a211-82aa-5df0c6a308d1@xxxxxxxxxx/T/#t

which has been acked and not merged yet.

> ---
>   include/linux/bpf_types.h | 2 ++
>   kernel/bpf/cgroup.c       | 6 ++++++
>   2 files changed, 8 insertions(+)
> 
> diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
> index eec5aeeeaf92..3c7222b2db96 100644
> --- a/include/linux/bpf_types.h
> +++ b/include/linux/bpf_types.h
> @@ -30,8 +30,10 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, raw_tracepoint_writable)
>   #ifdef CONFIG_CGROUP_BPF
>   BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev)
>   BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SYSCTL, cg_sysctl)
> +#ifdef CONFIG_NET
>   BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SOCKOPT, cg_sockopt)
>   #endif
> +#endif
>   #ifdef CONFIG_BPF_LIRC_MODE2
>   BPF_PROG_TYPE(BPF_PROG_TYPE_LIRC_MODE2, lirc_mode2)
>   #endif
> diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> index 76fa0076f20d..7be44460bd93 100644
> --- a/kernel/bpf/cgroup.c
> +++ b/kernel/bpf/cgroup.c
> @@ -590,6 +590,7 @@ int cgroup_bpf_prog_query(const union bpf_attr *attr,
>   	return ret;
>   }
>   
> +#ifdef CONFIG_NET
>   /**
>    * __cgroup_bpf_run_filter_skb() - Run a program for packet filtering
>    * @sk: The socket sending or receiving traffic
> @@ -750,6 +751,7 @@ int __cgroup_bpf_run_filter_sock_ops(struct sock *sk,
>   	return ret == 1 ? 0 : -EPERM;
>   }
>   EXPORT_SYMBOL(__cgroup_bpf_run_filter_sock_ops);
> +#endif
>   
>   int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,
>   				      short access, enum bpf_attach_type type)
> @@ -939,6 +941,7 @@ int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head,
>   }
>   EXPORT_SYMBOL(__cgroup_bpf_run_filter_sysctl);
>   
> +#ifdef CONFIG_NET
>   static bool __cgroup_bpf_prog_array_is_empty(struct cgroup *cgrp,
>   					     enum bpf_attach_type attach_type)
>   {
> @@ -1120,6 +1123,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
>   	return ret;
>   }
>   EXPORT_SYMBOL(__cgroup_bpf_run_filter_getsockopt);
> +#endif
>   
>   static ssize_t sysctl_cpy_dir(const struct ctl_dir *dir, char **bufp,
>   			      size_t *lenp)
> @@ -1382,6 +1386,7 @@ const struct bpf_verifier_ops cg_sysctl_verifier_ops = {
>   const struct bpf_prog_ops cg_sysctl_prog_ops = {
>   };
>   
> +#ifdef CONFIG_NET
>   static const struct bpf_func_proto *
>   cg_sockopt_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>   {
> @@ -1531,3 +1536,4 @@ const struct bpf_verifier_ops cg_sockopt_verifier_ops = {
>   
>   const struct bpf_prog_ops cg_sockopt_prog_ops = {
>   };
> +#endif
>