From: Daan De Meyer <daan.j.demeyer@xxxxxxxxx>
Date: Wed, 11 Oct 2023 19:03:12 +0200
> As prep for adding unix socket support to the cgroup sockaddr hooks,
> let's add a kfunc bpf_sock_addr_set_sun_path() that allows modifying a unix
> sockaddr from bpf. While this is already possible for AF_INET and AF_INET6,
> we'll need this kfunc when we add unix socket support since modifying the
> address for those requires modifying both the address and the sockaddr
> length.
>
> Signed-off-by: Daan De Meyer <daan.j.demeyer@xxxxxxxxx>
> ---
> kernel/bpf/btf.c | 1 +
> net/core/filter.c | 40 +++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 40 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 69101200c124..15d71d2986d3 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -7850,6 +7850,7 @@ static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type)
> case BPF_PROG_TYPE_SYSCALL:
> return BTF_KFUNC_HOOK_SYSCALL;
> case BPF_PROG_TYPE_CGROUP_SKB:
> + case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
> return BTF_KFUNC_HOOK_CGROUP_SKB;
> case BPF_PROG_TYPE_SCHED_ACT:
> return BTF_KFUNC_HOOK_SCHED_ACT;
> diff --git a/net/core/filter.c b/net/core/filter.c
> index a094694899c9..12fbd8a560c8 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -81,6 +81,7 @@
> #include <net/xdp.h>
> #include <net/mptcp.h>
> #include <net/netfilter/nf_conntrack_bpf.h>
> +#include <linux/un.h>
>
> static const struct bpf_func_proto *
> bpf_sk_base_func_proto(enum bpf_func_id func_id);
> @@ -11752,6 +11753,32 @@ __bpf_kfunc int bpf_dynptr_from_xdp(struct xdp_buff *xdp, u64 flags,
>
> return 0;
> }
> +
> +__bpf_kfunc int bpf_sock_addr_set_sun_path(struct bpf_sock_addr_kern *sa_kern,
> + const u8 *sun_path, u32 sun_path__sz)
> +{
> + struct sockaddr *sa = sa_kern->uaddr;
> + struct sockaddr_un *un;
> +
> + if (sa_kern->sk->sk_family != AF_UNIX)
> + return -EINVAL;
> +
> + /* We do not allow changing the address of unnamed unix sockets. */
> + if (sa_kern->uaddrlen == 0)
> + return -EINVAL;
Instead of adding this check, you can call the hooks after
unix_validate_addr() in connect() and sendmsg().
In unix_getname(), you can move up the bpf hooks into the else
branch below.
if (!addr) {
...
} else {
...
<-- here
}
> +
> + /* We do not allow changing the address to unnamed or larger than the
> + * maximum allowed address size for a unix sockaddr.
> + */
> + if (sun_path__sz == 0 || sun_path__sz > UNIX_PATH_MAX)
> + return -EINVAL;
> +
> + un = (struct sockaddr_un *)sa;
> + memcpy(un->sun_path, sun_path, sun_path__sz);
> + sa_kern->uaddrlen = offsetof(struct sockaddr_un, sun_path) + sun_path__sz;
> +
> + return 0;
> +}
> __diag_pop();
>
> int bpf_dynptr_from_skb_rdonly(struct sk_buff *skb, u64 flags,
> @@ -11776,6 +11803,10 @@ BTF_SET8_START(bpf_kfunc_check_set_xdp)
> BTF_ID_FLAGS(func, bpf_dynptr_from_xdp)
> BTF_SET8_END(bpf_kfunc_check_set_xdp)
>
> +BTF_SET8_START(bpf_kfunc_check_set_sock_addr)
> +BTF_ID_FLAGS(func, bpf_sock_addr_set_sun_path)
> +BTF_SET8_END(bpf_kfunc_check_set_sock_addr)
> +
> static const struct btf_kfunc_id_set bpf_kfunc_set_skb = {
> .owner = THIS_MODULE,
> .set = &bpf_kfunc_check_set_skb,
> @@ -11786,6 +11817,11 @@ static const struct btf_kfunc_id_set bpf_kfunc_set_xdp = {
> .set = &bpf_kfunc_check_set_xdp,
> };
>
> +static const struct btf_kfunc_id_set bpf_kfunc_set_sock_addr = {
> + .owner = THIS_MODULE,
> + .set = &bpf_kfunc_check_set_sock_addr,
> +};
> +
> static int __init bpf_kfunc_init(void)
> {
> int ret;
> @@ -11800,7 +11836,9 @@ static int __init bpf_kfunc_init(void)
> ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_XMIT, &bpf_kfunc_set_skb);
> ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_SEG6LOCAL, &bpf_kfunc_set_skb);
> ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_NETFILTER, &bpf_kfunc_set_skb);
> - return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &bpf_kfunc_set_xdp);
> + ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &bpf_kfunc_set_xdp);
> + return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
> + &bpf_kfunc_set_sock_addr);
> }
> late_initcall(bpf_kfunc_init);
>
> --
> 2.41.0
