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Date: Mon, 2 Oct 2017 16:48:52 -0700
From: Alexei Starovoitov <ast@...com>
To: "David S . Miller" <davem@...emloft.net>
CC: Daniel Borkmann <daniel@...earbox.net>, Tejun Heo <tj@...nel.org>,
David Ahern <dsa@...ulusnetworks.com>,
<netdev@...r.kernel.org>, <kernel-team@...com>
Subject: [PATCH net-next 3/8] bpf: enforce return code for cgroup-bpf programs
with addition of tnum logic the verifier got smart enough and
we can enforce return codes at program load time.
For now do so for cgroup-bpf program types.
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Acked-by: Daniel Borkmann <daniel@...earbox.net>
---
kernel/bpf/verifier.c | 40 ++++++++++++++++
tools/testing/selftests/bpf/test_verifier.c | 72 +++++++++++++++++++++++++++++
2 files changed, 112 insertions(+)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 4cf9b72c59a0..52b022310f6a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3073,6 +3073,43 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
return 0;
}
+static int check_return_code(struct bpf_verifier_env *env)
+{
+ struct bpf_reg_state *reg;
+ struct tnum range = tnum_range(0, 1);
+
+ switch (env->prog->type) {
+ case BPF_PROG_TYPE_CGROUP_SKB:
+ case BPF_PROG_TYPE_CGROUP_SOCK:
+ case BPF_PROG_TYPE_SOCK_OPS:
+ break;
+ default:
+ return 0;
+ }
+
+ reg = &env->cur_state.regs[BPF_REG_0];
+ if (reg->type != SCALAR_VALUE) {
+ verbose("At program exit the register R0 is not a known value (%s)\n",
+ reg_type_str[reg->type]);
+ return -EINVAL;
+ }
+
+ if (!tnum_in(range, reg->var_off)) {
+ verbose("At program exit the register R0 ");
+ if (!tnum_is_unknown(reg->var_off)) {
+ char tn_buf[48];
+
+ tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
+ verbose("has value %s", tn_buf);
+ } else {
+ verbose("has unknown scalar value");
+ }
+ verbose(" should have been 0 or 1\n");
+ return -EINVAL;
+ }
+ return 0;
+}
+
/* non-recursive DFS pseudo code
* 1 procedure DFS-iterative(G,v):
* 2 label v as discovered
@@ -3863,6 +3900,9 @@ static int do_check(struct bpf_verifier_env *env)
return -EACCES;
}
+ err = check_return_code(env);
+ if (err)
+ return err;
process_bpf_exit:
insn_idx = pop_stack(env, &prev_insn_idx);
if (insn_idx < 0) {
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 290d5056c165..cc91d0159f43 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -6892,6 +6892,78 @@ static struct bpf_test tests[] = {
.result = ACCEPT,
.prog_type = BPF_PROG_TYPE_XDP,
},
+ {
+ "bpf_exit with invalid return code. test1",
+ .insns = {
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1, 0),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "R0 has value (0x0; 0xffffffff)",
+ .result = REJECT,
+ .prog_type = BPF_PROG_TYPE_CGROUP_SOCK,
+ },
+ {
+ "bpf_exit with invalid return code. test2",
+ .insns = {
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1, 0),
+ BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ },
+ .result = ACCEPT,
+ .prog_type = BPF_PROG_TYPE_CGROUP_SOCK,
+ },
+ {
+ "bpf_exit with invalid return code. test3",
+ .insns = {
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1, 0),
+ BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 3),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "R0 has value (0x0; 0x3)",
+ .result = REJECT,
+ .prog_type = BPF_PROG_TYPE_CGROUP_SOCK,
+ },
+ {
+ "bpf_exit with invalid return code. test4",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ },
+ .result = ACCEPT,
+ .prog_type = BPF_PROG_TYPE_CGROUP_SOCK,
+ },
+ {
+ "bpf_exit with invalid return code. test5",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 2),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "R0 has value (0x2; 0x0)",
+ .result = REJECT,
+ .prog_type = BPF_PROG_TYPE_CGROUP_SOCK,
+ },
+ {
+ "bpf_exit with invalid return code. test6",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_0, BPF_REG_1),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "R0 is not a known value (ctx)",
+ .result = REJECT,
+ .prog_type = BPF_PROG_TYPE_CGROUP_SOCK,
+ },
+ {
+ "bpf_exit with invalid return code. test7",
+ .insns = {
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1, 0),
+ BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 4),
+ BPF_ALU64_REG(BPF_MUL, BPF_REG_0, BPF_REG_2),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "R0 has unknown scalar value",
+ .result = REJECT,
+ .prog_type = BPF_PROG_TYPE_CGROUP_SOCK,
+ },
};
static int probe_filter_length(const struct bpf_insn *fp)
--
2.9.5
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