[PATCH 5.10 04/23] selftests/bpf: Extend verifier and bpf_sock tests for dst_port loads

From: Greg Kroah-Hartman
Date: Tue Aug 09 2022 - 14:10:11 EST

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From: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>

commit 8f50f16ff39dd4e2d43d1548ca66925652f8aff7 upstream.

Add coverage to the verifier tests and tests for reading bpf_sock fields to
ensure that 32-bit, 16-bit, and 8-bit loads from dst_port field are allowed
only at intended offsets and produce expected values.

While 16-bit and 8-bit access to dst_port field is straight-forward, 32-bit
wide loads need be allowed and produce a zero-padded 16-bit value for
backward compatibility.

Signed-off-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220130115518.213259-3-jakub@xxxxxxxxxxxxxx
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
[OP: backport to 5.10: adjusted context in sock_fields.c]
Signed-off-by: Ovidiu Panait <ovidiu.panait@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
This series fixes the following bpf verfier selftest failures:
root@intel-x86-64:~# ./test_verifier
...
#908/u sk_fullsock(skb->sk): sk->dst_port [load 2nd byte] FAIL
#908/p sk_fullsock(skb->sk): sk->dst_port [load 2nd byte] FAIL

tools/include/uapi/linux/bpf.h | 3
tools/testing/selftests/bpf/prog_tests/sock_fields.c | 60 +++++++++-----
tools/testing/selftests/bpf/progs/test_sock_fields.c | 41 +++++++++
tools/testing/selftests/bpf/verifier/sock.c | 81 ++++++++++++++++++-
4 files changed, 162 insertions(+), 23 deletions(-)

--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4180,7 +4180,8 @@ struct bpf_sock {
__u32 src_ip4;
__u32 src_ip6[4];
__u32 src_port; /* host byte order */
- __u32 dst_port; /* network byte order */
+ __be16 dst_port; /* network byte order */
+ __u16 :16; /* zero padding */
__u32 dst_ip4;
__u32 dst_ip6[4];
__u32 state;
--- a/tools/testing/selftests/bpf/prog_tests/sock_fields.c
+++ b/tools/testing/selftests/bpf/prog_tests/sock_fields.c
@@ -1,9 +1,11 @@
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2019 Facebook */

+#define _GNU_SOURCE
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
+#include <sched.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
@@ -21,6 +23,7 @@
enum bpf_linum_array_idx {
EGRESS_LINUM_IDX,
INGRESS_LINUM_IDX,
+ READ_SK_DST_PORT_LINUM_IDX,
__NR_BPF_LINUM_ARRAY_IDX,
};

@@ -43,8 +46,16 @@ static __u64 child_cg_id;
static int linum_map_fd;
static __u32 duration;

-static __u32 egress_linum_idx = EGRESS_LINUM_IDX;
-static __u32 ingress_linum_idx = INGRESS_LINUM_IDX;
+static bool create_netns(void)
+{
+ if (!ASSERT_OK(unshare(CLONE_NEWNET), "create netns"))
+ return false;
+
+ if (!ASSERT_OK(system("ip link set dev lo up"), "bring up lo"))
+ return false;
+
+ return true;
+}

static void print_sk(const struct bpf_sock *sk, const char *prefix)
{
@@ -92,19 +103,24 @@ static void check_result(void)
{
struct bpf_tcp_sock srv_tp, cli_tp, listen_tp;
struct bpf_sock srv_sk, cli_sk, listen_sk;
- __u32 ingress_linum, egress_linum;
+ __u32 idx, ingress_linum, egress_linum, linum;
int err;

- err = bpf_map_lookup_elem(linum_map_fd, &egress_linum_idx,
- &egress_linum);
+ idx = EGRESS_LINUM_IDX;
+ err = bpf_map_lookup_elem(linum_map_fd, &idx, &egress_linum);
CHECK(err == -1, "bpf_map_lookup_elem(linum_map_fd)",
"err:%d errno:%d\n", err, errno);

- err = bpf_map_lookup_elem(linum_map_fd, &ingress_linum_idx,
- &ingress_linum);
+ idx = INGRESS_LINUM_IDX;
+ err = bpf_map_lookup_elem(linum_map_fd, &idx, &ingress_linum);
CHECK(err == -1, "bpf_map_lookup_elem(linum_map_fd)",
"err:%d errno:%d\n", err, errno);

+ idx = READ_SK_DST_PORT_LINUM_IDX;
+ err = bpf_map_lookup_elem(linum_map_fd, &idx, &linum);
+ ASSERT_OK(err, "bpf_map_lookup_elem(linum_map_fd, READ_SK_DST_PORT_IDX)");
+ ASSERT_EQ(linum, 0, "failure in read_sk_dst_port on line");
+
memcpy(&srv_sk, &skel->bss->srv_sk, sizeof(srv_sk));
memcpy(&srv_tp, &skel->bss->srv_tp, sizeof(srv_tp));
memcpy(&cli_sk, &skel->bss->cli_sk, sizeof(cli_sk));
@@ -263,7 +279,7 @@ static void test(void)
char buf[DATA_LEN];

/* Prepare listen_fd */
- listen_fd = start_server(AF_INET6, SOCK_STREAM, "::1", 0, 0);
+ listen_fd = start_server(AF_INET6, SOCK_STREAM, "::1", 0xcafe, 0);
/* start_server() has logged the error details */
if (CHECK_FAIL(listen_fd == -1))
goto done;
@@ -331,8 +347,12 @@ done:

void test_sock_fields(void)
{
- struct bpf_link *egress_link = NULL, *ingress_link = NULL;
int parent_cg_fd = -1, child_cg_fd = -1;
+ struct bpf_link *link;
+
+ /* Use a dedicated netns to have a fixed listen port */
+ if (!create_netns())
+ return;

/* Create a cgroup, get fd, and join it */
parent_cg_fd = test__join_cgroup(PARENT_CGROUP);
@@ -353,17 +373,20 @@ void test_sock_fields(void)
if (CHECK(!skel, "test_sock_fields__open_and_load", "failed\n"))
goto done;

- egress_link = bpf_program__attach_cgroup(skel->progs.egress_read_sock_fields,
- child_cg_fd);
- if (CHECK(IS_ERR(egress_link), "attach_cgroup(egress)", "err:%ld\n",
- PTR_ERR(egress_link)))
+ link = bpf_program__attach_cgroup(skel->progs.egress_read_sock_fields, child_cg_fd);
+ if (!ASSERT_OK_PTR(link, "attach_cgroup(egress_read_sock_fields)"))
+ goto done;
+ skel->links.egress_read_sock_fields = link;
+
+ link = bpf_program__attach_cgroup(skel->progs.ingress_read_sock_fields, child_cg_fd);
+ if (!ASSERT_OK_PTR(link, "attach_cgroup(ingress_read_sock_fields)"))
goto done;
+ skel->links.ingress_read_sock_fields = link;

- ingress_link = bpf_program__attach_cgroup(skel->progs.ingress_read_sock_fields,
- child_cg_fd);
- if (CHECK(IS_ERR(ingress_link), "attach_cgroup(ingress)", "err:%ld\n",
- PTR_ERR(ingress_link)))
+ link = bpf_program__attach_cgroup(skel->progs.read_sk_dst_port, child_cg_fd);
+ if (!ASSERT_OK_PTR(link, "attach_cgroup(read_sk_dst_port"))
goto done;
+ skel->links.read_sk_dst_port = link;

linum_map_fd = bpf_map__fd(skel->maps.linum_map);
sk_pkt_out_cnt_fd = bpf_map__fd(skel->maps.sk_pkt_out_cnt);
@@ -372,8 +395,7 @@ void test_sock_fields(void)
test();

done:
- bpf_link__destroy(egress_link);
- bpf_link__destroy(ingress_link);
+ test_sock_fields__detach(skel);
test_sock_fields__destroy(skel);
if (child_cg_fd != -1)
close(child_cg_fd);
--- a/tools/testing/selftests/bpf/progs/test_sock_fields.c
+++ b/tools/testing/selftests/bpf/progs/test_sock_fields.c
@@ -12,6 +12,7 @@
enum bpf_linum_array_idx {
EGRESS_LINUM_IDX,
INGRESS_LINUM_IDX,
+ READ_SK_DST_PORT_LINUM_IDX,
__NR_BPF_LINUM_ARRAY_IDX,
};

@@ -249,5 +250,45 @@ int ingress_read_sock_fields(struct __sk

return CG_OK;
}
+
+static __noinline bool sk_dst_port__load_word(struct bpf_sock *sk)
+{
+ __u32 *word = (__u32 *)&sk->dst_port;
+ return word[0] == bpf_htonl(0xcafe0000);
+}
+
+static __noinline bool sk_dst_port__load_half(struct bpf_sock *sk)
+{
+ __u16 *half = (__u16 *)&sk->dst_port;
+ return half[0] == bpf_htons(0xcafe);
+}
+
+static __noinline bool sk_dst_port__load_byte(struct bpf_sock *sk)
+{
+ __u8 *byte = (__u8 *)&sk->dst_port;
+ return byte[0] == 0xca && byte[1] == 0xfe;
+}
+
+SEC("cgroup_skb/egress")
+int read_sk_dst_port(struct __sk_buff *skb)
+{
+ __u32 linum, linum_idx;
+ struct bpf_sock *sk;
+
+ linum_idx = READ_SK_DST_PORT_LINUM_IDX;
+
+ sk = skb->sk;
+ if (!sk)
+ RET_LOG();
+
+ if (!sk_dst_port__load_word(sk))
+ RET_LOG();
+ if (!sk_dst_port__load_half(sk))
+ RET_LOG();
+ if (!sk_dst_port__load_byte(sk))
+ RET_LOG();
+
+ return CG_OK;
+}

char _license[] SEC("license") = "GPL";
--- a/tools/testing/selftests/bpf/verifier/sock.c
+++ b/tools/testing/selftests/bpf/verifier/sock.c
@@ -121,7 +121,25 @@
.result = ACCEPT,
},
{
- "sk_fullsock(skb->sk): sk->dst_port [narrow load]",
+ "sk_fullsock(skb->sk): sk->dst_port [word load] (backward compatibility)",
+ .insns = {
+ BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, offsetof(struct __sk_buff, sk)),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_1, 0, 2),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_0, offsetof(struct bpf_sock, dst_port)),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+ .result = ACCEPT,
+},
+{
+ "sk_fullsock(skb->sk): sk->dst_port [half load]",
.insns = {
BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, offsetof(struct __sk_buff, sk)),
BPF_JMP_IMM(BPF_JNE, BPF_REG_1, 0, 2),
@@ -139,7 +157,64 @@
.result = ACCEPT,
},
{
- "sk_fullsock(skb->sk): sk->dst_port [load 2nd byte]",
+ "sk_fullsock(skb->sk): sk->dst_port [half load] (invalid)",
+ .insns = {
+ BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, offsetof(struct __sk_buff, sk)),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_1, 0, 2),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_0, offsetof(struct bpf_sock, dst_port) + 2),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+ .result = REJECT,
+ .errstr = "invalid sock access",
+},
+{
+ "sk_fullsock(skb->sk): sk->dst_port [byte load]",
+ .insns = {
+ BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, offsetof(struct __sk_buff, sk)),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_1, 0, 2),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ BPF_LDX_MEM(BPF_B, BPF_REG_2, BPF_REG_0, offsetof(struct bpf_sock, dst_port)),
+ BPF_LDX_MEM(BPF_B, BPF_REG_2, BPF_REG_0, offsetof(struct bpf_sock, dst_port) + 1),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+ .result = ACCEPT,
+},
+{
+ "sk_fullsock(skb->sk): sk->dst_port [byte load] (invalid)",
+ .insns = {
+ BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, offsetof(struct __sk_buff, sk)),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_1, 0, 2),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_0, offsetof(struct bpf_sock, dst_port) + 2),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+ .result = REJECT,
+ .errstr = "invalid sock access",
+},
+{
+ "sk_fullsock(skb->sk): past sk->dst_port [half load] (invalid)",
.insns = {
BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, offsetof(struct __sk_buff, sk)),
BPF_JMP_IMM(BPF_JNE, BPF_REG_1, 0, 2),
@@ -149,7 +224,7 @@
BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
- BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_0, offsetof(struct bpf_sock, dst_port) + 1),
+ BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_0, offsetofend(struct bpf_sock, dst_port)),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},

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