selftests/bpf: Test sysctl_get_current_value helper

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>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/test_sysctl.c b/tools/testing/selftests/bpf/test_sysctl.c
index 2e7ef04..9fb6560 100644 (file)
--- 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"