[bpf-next,v3,3/9] bpf: Add bpf_sock_addr_set_unix_addr() to allow writing unix sockaddr from bpf

Commit Message

Daan De Meyer Aug. 31, 2023, 3:34 p.m. UTC

As prep for adding unix socket support to the cgroup sockaddr hooks,
let's add a kfunc bpf_sock_addr_set_unix_addr() that allows modifying a 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 <[e-mail]>
---
 kernel/bpf/btf.c  |  1 +
 net/core/filter.c | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

Comments

Alexei Starovoitov Sept. 4, 2023, 8:58 p.m. UTC | #1

On Thu, Aug 31, 2023 at 8:36 AM Daan De Meyer <[e-mail]> wrote:
>
> As prep for adding unix socket support to the cgroup sockaddr hooks,
> let's add a kfunc bpf_sock_addr_set_unix_addr() that allows modifying a 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 <[e-mail]>
> ---
>  kernel/bpf/btf.c  |  1 +
>  net/core/filter.c | 32 +++++++++++++++++++++++++++++++-
>  2 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 249657c466dd..15c972f27574 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -7819,6 +7819,7 @@ static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type)
>  {
>         switch (prog_type) {
>         case BPF_PROG_TYPE_UNSPEC:
> +       case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
>                 return BTF_KFUNC_HOOK_COMMON;

hook_common means that they are shared by all prog types.
See btf_kfunc_id_set_contains().

Martin KaFai Lau Sept. 5, 2023, 9:37 p.m. UTC | #2

On 8/31/23 8:34 AM, Daan De Meyer wrote:
> As prep for adding unix socket support to the cgroup sockaddr hooks,
> let's add a kfunc bpf_sock_addr_set_unix_addr() that allows modifying a 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 <[e-mail]>
> ---
>   kernel/bpf/btf.c  |  1 +
>   net/core/filter.c | 32 +++++++++++++++++++++++++++++++-
>   2 files changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 249657c466dd..15c972f27574 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -7819,6 +7819,7 @@ static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type)
>   {
>   	switch (prog_type) {
>   	case BPF_PROG_TYPE_UNSPEC:
> +	case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
>   		return BTF_KFUNC_HOOK_COMMON;
>   	case BPF_PROG_TYPE_XDP:
>   		return BTF_KFUNC_HOOK_XDP;
> diff --git a/net/core/filter.c b/net/core/filter.c
> index a094694899c9..3ed6cd33b268 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -11752,6 +11752,25 @@ __bpf_kfunc int bpf_dynptr_from_xdp(struct xdp_buff *xdp, u64 flags,
>   
>   	return 0;
>   }
> +
> +__bpf_kfunc int bpf_sock_addr_set_unix_addr(struct bpf_sock_addr_kern *sa_kern,
> +					    const u8 *addr, u32 addrlen__sz)
> +{
> +	struct sockaddr *sa = sa_kern->uaddr;
> +	struct sockaddr_un *un;
> +
> +	if (sa_kern->sk->sk_family != AF_UNIX)
> +		return -EINVAL;
> +
> +	if (addrlen__sz > UNIX_PATH_MAX)

Is it valid to have addrlen__sz == 0 for AF_UNIX?

> +		return -EINVAL;
> +
> +	un = (struct sockaddr_un *)sa;
> +	memcpy(un->sun_path, addr, addrlen__sz);
> +	sa_kern->uaddrlen = offsetof(struct sockaddr_un, sun_path) + addrlen__sz;
> +
> +	return 0;
> +}

Patch

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 249657c466dd..15c972f27574 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -7819,6 +7819,7 @@  static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type)
 {
 	switch (prog_type) {
 	case BPF_PROG_TYPE_UNSPEC:
+	case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
 		return BTF_KFUNC_HOOK_COMMON;
 	case BPF_PROG_TYPE_XDP:
 		return BTF_KFUNC_HOOK_XDP;
diff --git a/net/core/filter.c b/net/core/filter.c
index a094694899c9..3ed6cd33b268 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -11752,6 +11752,25 @@  __bpf_kfunc int bpf_dynptr_from_xdp(struct xdp_buff *xdp, u64 flags,
 
 	return 0;
 }
+
+__bpf_kfunc int bpf_sock_addr_set_unix_addr(struct bpf_sock_addr_kern *sa_kern,
+					    const u8 *addr, u32 addrlen__sz)
+{
+	struct sockaddr *sa = sa_kern->uaddr;
+	struct sockaddr_un *un;
+
+	if (sa_kern->sk->sk_family != AF_UNIX)
+		return -EINVAL;
+
+	if (addrlen__sz > UNIX_PATH_MAX)
+		return -EINVAL;
+
+	un = (struct sockaddr_un *)sa;
+	memcpy(un->sun_path, addr, addrlen__sz);
+	sa_kern->uaddrlen = offsetof(struct sockaddr_un, sun_path) + addrlen__sz;
+
+	return 0;
+}
 __diag_pop();
 
 int bpf_dynptr_from_skb_rdonly(struct sk_buff *skb, u64 flags,
@@ -11776,6 +11795,10 @@  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_unix_addr)
+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 +11809,11 @@  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 +11828,9 @@  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);