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Subject[PATCH v3 bpf-next 12/21] selftests/bpf: Test sysctl_get_current_value helper
Date
Test sysctl_get_current_value on sysctl read and write, buffers with
enough space and too small buffers to get E2BIG and truncated result,
etc.

# ./test_sysctl
...
Test case: sysctl_get_current_value sysctl:read ok, gt .. [PASS]
Test case: sysctl_get_current_value sysctl:read ok, eq .. [PASS]
Test case: sysctl_get_current_value sysctl:read E2BIG truncated .. [PASS]
Test case: sysctl_get_current_value sysctl:read EINVAL .. [PASS]
Test case: sysctl_get_current_value sysctl:write ok .. [PASS]
Summary: 16 PASSED, 0 FAILED

Signed-off-by: Andrey Ignatov <rdna@fb.com>
---
tools/testing/selftests/bpf/test_sysctl.c | 228 ++++++++++++++++++++++
1 file changed, 228 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_sysctl.c b/tools/testing/selftests/bpf/test_sysctl.c
index 2e7ef04503a8..9fb6560fa775 100644
--- a/tools/testing/selftests/bpf/test_sysctl.c
+++ b/tools/testing/selftests/bpf/test_sysctl.c
@@ -18,11 +18,13 @@

#define CG_PATH "/foo"
#define MAX_INSNS 512
+#define FIXUP_SYSCTL_VALUE 0

char bpf_log_buf[BPF_LOG_BUF_SIZE];

struct sysctl_test {
const char *descr;
+ size_t fixup_value_insn;
struct bpf_insn insns[MAX_INSNS];
enum bpf_attach_type attach_type;
const char *sysctl;
@@ -350,6 +352,190 @@ static struct sysctl_test tests[] = {
.open_flags = O_RDONLY,
.result = SUCCESS,
},
+ {
+ .descr = "sysctl_get_current_value sysctl:read ok, gt",
+ .insns = {
+ /* sysctl_get_current_value arg2 (buf) */
+ BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_7),
+
+ /* sysctl_get_current_value arg3 (buf_len) */
+ BPF_MOV64_IMM(BPF_REG_3, 8),
+
+ /* sysctl_get_current_value(ctx, buf, buf_len) */
+ BPF_EMIT_CALL(BPF_FUNC_sysctl_get_current_value),
+
+ /* if (ret == expected && */
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 6, 6),
+
+ /* buf[0:6] == "Linux\n\0") */
+ BPF_LD_IMM64(BPF_REG_8, 0x000a78756e694cULL),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0),
+ BPF_JMP_REG(BPF_JNE, BPF_REG_8, BPF_REG_9, 2),
+
+ /* return ALLOW; */
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_JMP_A(1),
+
+ /* else return DENY; */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "kernel/ostype",
+ .open_flags = O_RDONLY,
+ .result = SUCCESS,
+ },
+ {
+ .descr = "sysctl_get_current_value sysctl:read ok, eq",
+ .insns = {
+ /* sysctl_get_current_value arg2 (buf) */
+ BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_STX_MEM(BPF_B, BPF_REG_7, BPF_REG_0, 7),
+
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_7),
+
+ /* sysctl_get_current_value arg3 (buf_len) */
+ BPF_MOV64_IMM(BPF_REG_3, 7),
+
+ /* sysctl_get_current_value(ctx, buf, buf_len) */
+ BPF_EMIT_CALL(BPF_FUNC_sysctl_get_current_value),
+
+ /* if (ret == expected && */
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 6, 6),
+
+ /* buf[0:6] == "Linux\n\0") */
+ BPF_LD_IMM64(BPF_REG_8, 0x000a78756e694cULL),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0),
+ BPF_JMP_REG(BPF_JNE, BPF_REG_8, BPF_REG_9, 2),
+
+ /* return ALLOW; */
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_JMP_A(1),
+
+ /* else return DENY; */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "kernel/ostype",
+ .open_flags = O_RDONLY,
+ .result = SUCCESS,
+ },
+ {
+ .descr = "sysctl_get_current_value sysctl:read E2BIG truncated",
+ .insns = {
+ /* sysctl_get_current_value arg2 (buf) */
+ BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_STX_MEM(BPF_H, BPF_REG_7, BPF_REG_0, 6),
+
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_7),
+
+ /* sysctl_get_current_value arg3 (buf_len) */
+ BPF_MOV64_IMM(BPF_REG_3, 6),
+
+ /* sysctl_get_current_value(ctx, buf, buf_len) */
+ BPF_EMIT_CALL(BPF_FUNC_sysctl_get_current_value),
+
+ /* if (ret == expected && */
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, -E2BIG, 6),
+
+ /* buf[0:6] == "Linux\0") */
+ BPF_LD_IMM64(BPF_REG_8, 0x000078756e694cULL),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0),
+ BPF_JMP_REG(BPF_JNE, BPF_REG_8, BPF_REG_9, 2),
+
+ /* return ALLOW; */
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_JMP_A(1),
+
+ /* else return DENY; */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "kernel/ostype",
+ .open_flags = O_RDONLY,
+ .result = SUCCESS,
+ },
+ {
+ .descr = "sysctl_get_current_value sysctl:read EINVAL",
+ .insns = {
+ /* sysctl_get_current_value arg2 (buf) */
+ BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_7),
+
+ /* sysctl_get_current_value arg3 (buf_len) */
+ BPF_MOV64_IMM(BPF_REG_3, 8),
+
+ /* sysctl_get_current_value(ctx, buf, buf_len) */
+ BPF_EMIT_CALL(BPF_FUNC_sysctl_get_current_value),
+
+ /* if (ret == expected && */
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, -EINVAL, 4),
+
+ /* buf[0:8] is NUL-filled) */
+ BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_9, 0, 2),
+
+ /* return DENY; */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_JMP_A(1),
+
+ /* else return ALLOW; */
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "net/ipv6/conf/lo/stable_secret", /* -EIO */
+ .open_flags = O_RDONLY,
+ .result = OP_EPERM,
+ },
+ {
+ .descr = "sysctl_get_current_value sysctl:write ok",
+ .fixup_value_insn = 6,
+ .insns = {
+ /* sysctl_get_current_value arg2 (buf) */
+ BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_7),
+
+ /* sysctl_get_current_value arg3 (buf_len) */
+ BPF_MOV64_IMM(BPF_REG_3, 8),
+
+ /* sysctl_get_current_value(ctx, buf, buf_len) */
+ BPF_EMIT_CALL(BPF_FUNC_sysctl_get_current_value),
+
+ /* if (ret == expected && */
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 4, 6),
+
+ /* buf[0:4] == expected) */
+ BPF_LD_IMM64(BPF_REG_8, FIXUP_SYSCTL_VALUE),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0),
+ BPF_JMP_REG(BPF_JNE, BPF_REG_8, BPF_REG_9, 2),
+
+ /* return DENY; */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_JMP_A(1),
+
+ /* else return ALLOW; */
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "net/ipv4/route/mtu_expires",
+ .open_flags = O_WRONLY,
+ .newval = "600", /* same as default, should fail anyway */
+ .result = OP_EPERM,
+ },
};

static size_t probe_prog_length(const struct bpf_insn *fp)
@@ -362,6 +548,27 @@ static size_t probe_prog_length(const struct bpf_insn *fp)
return len + 1;
}

+static int fixup_sysctl_value(const char *buf, size_t buf_len,
+ struct bpf_insn *prog, size_t insn_num)
+{
+ uint32_t value_num = 0;
+ uint8_t c, i;
+
+ if (buf_len > sizeof(value_num)) {
+ log_err("Value is too big (%zd) to use in fixup", buf_len);
+ return -1;
+ }
+
+ for (i = 0; i < buf_len; ++i) {
+ c = buf[i];
+ value_num |= (c << i * 8);
+ }
+
+ prog[insn_num].imm = value_num;
+
+ return 0;
+}
+
static int load_sysctl_prog(struct sysctl_test *test, const char *sysctl_path)
{
struct bpf_insn *prog = test->insns;
@@ -374,6 +581,27 @@ static int load_sysctl_prog(struct sysctl_test *test, const char *sysctl_path)
attr.insns_cnt = probe_prog_length(attr.insns);
attr.license = "GPL";

+ if (test->fixup_value_insn) {
+ char buf[128];
+ ssize_t len;
+ int fd;
+
+ fd = open(sysctl_path, O_RDONLY | O_CLOEXEC);
+ if (fd < 0) {
+ log_err("open(%s) failed", sysctl_path);
+ return -1;
+ }
+ len = read(fd, buf, sizeof(buf));
+ if (len == -1) {
+ log_err("read(%s) failed", sysctl_path);
+ close(fd);
+ return -1;
+ }
+ close(fd);
+ if (fixup_sysctl_value(buf, len, prog, test->fixup_value_insn))
+ return -1;
+ }
+
ret = bpf_load_program_xattr(&attr, bpf_log_buf, BPF_LOG_BUF_SIZE);
if (ret < 0 && test->result != LOAD_REJECT) {
log_err(">>> Loading program error.\n"
--
2.17.1
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