bpf: Change bpf_sk_release and bpf_sk_*cgroup_id to accept ARG_PTR_TO_BTF_ID_SOCK_COMMON

The previous patch allows the networking bpf prog to use the
bpf_skc_to_*() helpers to get a PTR_TO_BTF_ID socket pointer,
e.g. "struct tcp_sock *".  It allows the bpf prog to read all the
fields of the tcp_sock.

This patch changes the bpf_sk_release() and bpf_sk_*cgroup_id()
to take ARG_PTR_TO_BTF_ID_SOCK_COMMON such that they will
work with the pointer returned by the bpf_skc_to_*() helpers
also.  For example, the following will work:

	sk = bpf_skc_lookup_tcp(skb, tuple, tuplen, BPF_F_CURRENT_NETNS, 0);
	if (!sk)
		return;
	tp = bpf_skc_to_tcp_sock(sk);
	if (!tp) {
		bpf_sk_release(sk);
		return;
	}
	lsndtime = tp->lsndtime;
	/* Pass tp to bpf_sk_release() will also work */
	bpf_sk_release(tp);

Since PTR_TO_BTF_ID could be NULL, the helper taking
ARG_PTR_TO_BTF_ID_SOCK_COMMON has to check for NULL at runtime.

A btf_id of "struct sock" may not always mean a fullsock.  Regardless
the helper's running context may get a non-fullsock or not,
considering fullsock check/handling is pretty cheap, it is better to
keep the same verifier expectation on helper that takes ARG_PTR_TO_BTF_ID*
will be able to handle the minisock situation.  In the bpf_sk_*cgroup_id()
case,  it will try to get a fullsock by using sk_to_full_sk() as its
skb variant bpf_sk"b"_*cgroup_id() has already been doing.

bpf_sk_release can already handle minisock, so nothing special has to
be done.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200925000356.3856047-1-kafai@fb.com

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index a228125..c96a56d 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2512,7 +2512,7 @@ union bpf_attr {
  *             result is from *reuse*\ **->socks**\ [] using the hash of the
  *             tuple.
  *
- * long bpf_sk_release(struct bpf_sock *sock)
+ * long bpf_sk_release(void *sock)
  *     Description
  *             Release the reference held by *sock*. *sock* must be a
  *             non-**NULL** pointer that was returned from
@@ -3234,11 +3234,11 @@ union bpf_attr {
  *
  *             **-EOVERFLOW** if an overflow happened: The same object will be tried again.
  *
- * u64 bpf_sk_cgroup_id(struct bpf_sock *sk)
+ * u64 bpf_sk_cgroup_id(void *sk)
  *     Description
  *             Return the cgroup v2 id of the socket *sk*.
  *
- *             *sk* must be a non-**NULL** pointer to a full socket, e.g. one
+ *             *sk* must be a non-**NULL** pointer to a socket, e.g. one
  *             returned from **bpf_sk_lookup_xxx**\ (),
  *             **bpf_sk_fullsock**\ (), etc. The format of returned id is
  *             same as in **bpf_skb_cgroup_id**\ ().
@@ -3248,7 +3248,7 @@ union bpf_attr {
  *     Return
  *             The id is returned or 0 in case the id could not be retrieved.
  *
- * u64 bpf_sk_ancestor_cgroup_id(struct bpf_sock *sk, int ancestor_level)
+ * u64 bpf_sk_ancestor_cgroup_id(void *sk, int ancestor_level)
  *     Description
  *             Return id of cgroup v2 that is ancestor of cgroup associated
  *             with the *sk* at the *ancestor_level*.  The root cgroup is at

diff --git a/net/core/filter.c b/net/core/filter.c
index 6d1864f..06d397e 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4088,18 +4088,17 @@ static inline u64 __bpf_sk_cgroup_id(struct sock *sk)
 {
        struct cgroup *cgrp;
 
+       sk = sk_to_full_sk(sk);
+       if (!sk || !sk_fullsock(sk))
+               return 0;
+
        cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
        return cgroup_id(cgrp);
 }
 
 BPF_CALL_1(bpf_skb_cgroup_id, const struct sk_buff *, skb)
 {
-       struct sock *sk = skb_to_full_sk(skb);
-
-       if (!sk || !sk_fullsock(sk))
-               return 0;
-
-       return __bpf_sk_cgroup_id(sk);
+       return __bpf_sk_cgroup_id(skb->sk);
 }
 
 static const struct bpf_func_proto bpf_skb_cgroup_id_proto = {
@@ -4115,6 +4114,10 @@ static inline u64 __bpf_sk_ancestor_cgroup_id(struct sock *sk,
        struct cgroup *ancestor;
        struct cgroup *cgrp;
 
+       sk = sk_to_full_sk(sk);
+       if (!sk || !sk_fullsock(sk))
+               return 0;
+
        cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
        ancestor = cgroup_ancestor(cgrp, ancestor_level);
        if (!ancestor)
@@ -4126,12 +4129,7 @@ static inline u64 __bpf_sk_ancestor_cgroup_id(struct sock *sk,
 BPF_CALL_2(bpf_skb_ancestor_cgroup_id, const struct sk_buff *, skb, int,
           ancestor_level)
 {
-       struct sock *sk = skb_to_full_sk(skb);
-
-       if (!sk || !sk_fullsock(sk))
-               return 0;
-
-       return __bpf_sk_ancestor_cgroup_id(sk, ancestor_level);
+       return __bpf_sk_ancestor_cgroup_id(skb->sk, ancestor_level);
 }
 
 static const struct bpf_func_proto bpf_skb_ancestor_cgroup_id_proto = {
@@ -4151,7 +4149,7 @@ static const struct bpf_func_proto bpf_sk_cgroup_id_proto = {
        .func           = bpf_sk_cgroup_id,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
-       .arg1_type      = ARG_PTR_TO_SOCKET,
+       .arg1_type      = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
 };
 
 BPF_CALL_2(bpf_sk_ancestor_cgroup_id, struct sock *, sk, int, ancestor_level)
@@ -4163,7 +4161,7 @@ static const struct bpf_func_proto bpf_sk_ancestor_cgroup_id_proto = {
        .func           = bpf_sk_ancestor_cgroup_id,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
-       .arg1_type      = ARG_PTR_TO_SOCKET,
+       .arg1_type      = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
        .arg2_type      = ARG_ANYTHING,
 };
 #endif
@@ -5697,7 +5695,7 @@ static const struct bpf_func_proto bpf_sk_lookup_udp_proto = {
 
 BPF_CALL_1(bpf_sk_release, struct sock *, sk)
 {
-       if (sk_is_refcounted(sk))
+       if (sk && sk_is_refcounted(sk))
                sock_gen_put(sk);
        return 0;
 }
@@ -5706,7 +5704,7 @@ static const struct bpf_func_proto bpf_sk_release_proto = {
        .func           = bpf_sk_release,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
-       .arg1_type      = ARG_PTR_TO_SOCK_COMMON,
+       .arg1_type      = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
 };
 
 BPF_CALL_5(bpf_xdp_sk_lookup_udp, struct xdp_buff *, ctx,

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index a228125..c96a56d 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -2512,7 +2512,7 @@ union bpf_attr {
  *             result is from *reuse*\ **->socks**\ [] using the hash of the
  *             tuple.
  *
- * long bpf_sk_release(struct bpf_sock *sock)
+ * long bpf_sk_release(void *sock)
  *     Description
  *             Release the reference held by *sock*. *sock* must be a
  *             non-**NULL** pointer that was returned from
@@ -3234,11 +3234,11 @@ union bpf_attr {
  *
  *             **-EOVERFLOW** if an overflow happened: The same object will be tried again.
  *
- * u64 bpf_sk_cgroup_id(struct bpf_sock *sk)
+ * u64 bpf_sk_cgroup_id(void *sk)
  *     Description
  *             Return the cgroup v2 id of the socket *sk*.
  *
- *             *sk* must be a non-**NULL** pointer to a full socket, e.g. one
+ *             *sk* must be a non-**NULL** pointer to a socket, e.g. one
  *             returned from **bpf_sk_lookup_xxx**\ (),
  *             **bpf_sk_fullsock**\ (), etc. The format of returned id is
  *             same as in **bpf_skb_cgroup_id**\ ().
@@ -3248,7 +3248,7 @@ union bpf_attr {
  *     Return
  *             The id is returned or 0 in case the id could not be retrieved.
  *
- * u64 bpf_sk_ancestor_cgroup_id(struct bpf_sock *sk, int ancestor_level)
+ * u64 bpf_sk_ancestor_cgroup_id(void *sk, int ancestor_level)
  *     Description
  *             Return id of cgroup v2 that is ancestor of cgroup associated
  *             with the *sk* at the *ancestor_level*.  The root cgroup is at