Subject: [PATCH bpf-next 1/2] bpf: expose socket storage to BPF_PROG_TYPE_CGROUP_SOCK

From: Stanislav Fomichev <[email-masked]>
Date: Tue, 28 Jul 2020 17:31:03 -0700

This lets us use socket storage from the following hooks:
* BPF_CGROUP_INET_SOCK_CREATE
* BPF_CGROUP_INET_SOCK_RELEASE
* BPF_CGROUP_INET4_POST_BIND
* BPF_CGROUP_INET6_POST_BIND

Using existing 'bpf_sk_storage_get_proto' doesn't work because
second argument is ARG_PTR_TO_SOCKET. Even though
BPF_PROG_TYPE_CGROUP_SOCK hooks operate on 'struct bpf_sock',
the verifier still considers it as a PTR_TO_CTX.
That's why I'm adding another 'bpf_sk_storage_get_cg_sock_proto'
definition strictly for BPF_PROG_TYPE_CGROUP_SOCK which accepts
ARG_PTR_TO_CTX which is really 'struct sock' for this program type.

Cc: Martin KaFai Lau <[email-masked]>
Signed-off-by: Stanislav Fomichev <[email-masked]>
---
 net/core/bpf_sk_storage.c | 10 ++++++++++
 net/core/filter.c         |  3 +++
 2 files changed, 13 insertions(+)

diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index eafcd15e7dfd..d3377c90a291 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -944,6 +944,16 @@ const struct bpf_func_proto bpf_sk_storage_get_proto = {
 	.arg4_type	= ARG_ANYTHING,
 };
 
+const struct bpf_func_proto bpf_sk_storage_get_cg_sock_proto = {
+	.func		= bpf_sk_storage_get,
+	.gpl_only	= false,
+	.ret_type	= RET_PTR_TO_MAP_VALUE_OR_NULL,
+	.arg1_type	= ARG_CONST_MAP_PTR,
+	.arg2_type	= ARG_PTR_TO_CTX, /* context is 'struct sock' */
+	.arg3_type	= ARG_PTR_TO_MAP_VALUE_OR_NULL,
+	.arg4_type	= ARG_ANYTHING,
+};
+
 const struct bpf_func_proto bpf_sk_storage_delete_proto = {
 	.func		= bpf_sk_storage_delete,
 	.gpl_only	= false,
diff --git a/net/core/filter.c b/net/core/filter.c
index 29e3455122f7..7124f0fe6974 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6187,6 +6187,7 @@ bool bpf_helper_changes_pkt_data(void *func)
 }
 
 const struct bpf_func_proto bpf_event_output_data_proto __weak;
+const struct bpf_func_proto bpf_sk_storage_get_cg_sock_proto __weak;
 
 static const struct bpf_func_proto *
 sock_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
@@ -6219,6 +6220,8 @@ sock_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_get_cgroup_classid:
 		return &bpf_get_cgroup_classid_curr_proto;
 #endif
+	case BPF_FUNC_sk_storage_get:
+		return &bpf_sk_storage_get_cg_sock_proto;
 	default:
 		return bpf_base_func_proto(func_id);
 	}
-- 
2.28.0.163.g6104cc2f0b6-goog