samples/bpf: Update cgroup socket examples to use uid gid helper

This change “samples/bpf: Update cgroup socket examples to use uid gid helper” (commit 0adc3dd) in Linux kernel is authored by David Ahern <dsahern [at] gmail.com> on Thu Aug 31 15:05:50 2017 -0700.

Description of "samples/bpf: Update cgroup socket examples to use uid gid helper"

The change “samples/bpf: Update cgroup socket examples to use uid gid helper” introduces changes as follows.

samples/bpf: Update cgroup socket examples to use uid gid helper

Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Linux kernel releases containing commit 0adc3dd

The Linux kernel releases containing this commit are as follows.

Linux kernel code changes from "samples/bpf: Update cgroup socket examples to use uid gid helper"

There are 17 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 samples/bpf/sock_flags_kern.c |  5 +++++
 samples/bpf/test_cgrp2_sock.c | 12 +++++++++++-
 2 files changed, 16 insertions(+), 1 deletion(-)
 
diff --git a/samples/bpf/sock_flags_kern.c b/samples/bpf/sock_flags_kern.c
index 533dd11a6baa..05dcdf8a4baa 100644
--- a/samples/bpf/sock_flags_kern.c
+++ b/samples/bpf/sock_flags_kern.c
@@ -9,8 +9,13 @@ SEC("cgroup/sock1")
 int bpf_prog1(struct bpf_sock *sk)
 {
 	char fmt[] = "socket: family %d type %d protocol %d\n";
+	char fmt2[] = "socket: uid %u gid %u\n";
+	__u64 gid_uid = bpf_get_current_uid_gid();
+	__u32 uid = gid_uid & 0xffffffff;
+	__u32 gid = gid_uid >> 32;
 
 	bpf_trace_printk(fmt, sizeof(fmt), sk->family, sk->type, sk->protocol);
+	bpf_trace_printk(fmt2, sizeof(fmt2), uid, gid);
 
 	/* block PF_INET6, SOCK_RAW, IPPROTO_ICMPV6 sockets
 	 * ie., make ping6 fail
diff --git a/samples/bpf/test_cgrp2_sock.c b/samples/bpf/test_cgrp2_sock.c
index 5a688837720c..e79594dd629b 100644
--- a/samples/bpf/test_cgrp2_sock.c
+++ b/samples/bpf/test_cgrp2_sock.c
@@ -46,8 +46,18 @@ static int prog_load(__u32 idx, __u32 mark, __u32 prio)
 
 	/* set mark on socket */
 	struct bpf_insn prog_mark[] = {
-		BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
+		/* get uid of process */
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+			     BPF_FUNC_get_current_uid_gid),
+		BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0xffffffff),
+
+		/* if uid is 0, use given mark, else use the uid as the mark */
+		BPF_MOV64_REG(BPF_REG_3, BPF_REG_0),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
 		BPF_MOV64_IMM(BPF_REG_3, mark),
+
+		/* set the mark on the new socket */
+		BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
 		BPF_MOV64_IMM(BPF_REG_2, offsetof(struct bpf_sock, mark)),
 		BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_3, offsetof(struct bpf_sock, mark)),
 	};

The commit for this change in Linux stable tree is 0adc3dd (patch).

Last modified: 2020/02/09