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bpf: Change bpf_sk_release and bpf_sk_*cgroup_id to accept ARG_PTR_TO_BTF_ID_SOCK_COMMON

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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
This commit is contained in:
Martin KaFai Lau
2020-09-24 17:03:56 -07:00
committed by Alexei Starovoitov
parent 1df8f55a37
commit a5fa25adf0
3 changed files with 22 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
include/uapi/linux/bpf.h
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@@ -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