selftests/bpf: add a test for verifier logs

Add a test for verifier log handling.  Check bad attr combinations
but focus on cases when log is truncated.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/bpf/Makefile

@@ -12,7 +12,7 @@ CFLAGS += -Wall -O2 -I$(APIDIR) -I$(LIBDIR) -I$(GENDIR) $(GENFLAGS) -I../../../i
 LDLIBS += -lcap -lelf
 
 TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \
-	test_align
+	test_align test_verifier_log
 
 TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test_obj_id.o \
 	test_pkt_md_access.o test_xdp_redirect.o test_xdp_meta.o sockmap_parse_prog.o     \

tools/testing/selftests/bpf/test_verifier_log.c

@@ -0,0 +1,171 @@
+#include <errno.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <linux/bpf.h>
+#include <linux/filter.h>
+#include <linux/unistd.h>
+
+#include <bpf/bpf.h>
+
+#define LOG_SIZE (1 << 20)
+
+#define err(str...)	printf("ERROR: " str)
+
+static const struct bpf_insn code_sample[] = {
+	/* We need a few instructions to pass the min log length */
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+		     BPF_FUNC_map_lookup_elem),
+	BPF_EXIT_INSN(),
+};
+
+static inline __u64 ptr_to_u64(const void *ptr)
+{
+	return (__u64) (unsigned long) ptr;
+}
+
+static int load(char *log, size_t log_len, int log_level)
+{
+	union bpf_attr attr;
+
+	bzero(&attr, sizeof(attr));
+	attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
+	attr.insn_cnt = (__u32)(sizeof(code_sample) / sizeof(struct bpf_insn));
+	attr.insns = ptr_to_u64(code_sample);
+	attr.license = ptr_to_u64("GPL");
+	attr.log_buf = ptr_to_u64(log);
+	attr.log_size = log_len;
+	attr.log_level = log_level;
+
+	return syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr));
+}
+
+static void check_ret(int ret, int exp_errno)
+{
+	if (ret > 0) {
+		close(ret);
+		err("broken sample loaded successfully!?\n");
+		exit(1);
+	}
+
+	if (!ret || errno != exp_errno) {
+		err("Program load returned: ret:%d/errno:%d, expected ret:%d/errno:%d\n",
+		    ret, errno, -1, exp_errno);
+		exit(1);
+	}
+}
+
+static void check_ones(const char *buf, size_t len, const char *msg)
+{
+	while (len--)
+		if (buf[len] != 1) {
+			err("%s", msg);
+			exit(1);
+		}
+}
+
+static void test_log_good(char *log, size_t buf_len, size_t log_len,
+			  size_t exp_len, int exp_errno, const char *full_log)
+{
+	size_t len;
+	int ret;
+
+	memset(log, 1, buf_len);
+
+	ret = load(log, log_len, 1);
+	check_ret(ret, exp_errno);
+
+	len = strnlen(log, buf_len);
+	if (len == buf_len) {
+		err("verifier did not NULL terminate the log\n");
+		exit(1);
+	}
+	if (exp_len && len != exp_len) {
+		err("incorrect log length expected:%zd have:%zd\n",
+		    exp_len, len);
+		exit(1);
+	}
+
+	if (strchr(log, 1)) {
+		err("verifier leaked a byte through\n");
+		exit(1);
+	}
+
+	check_ones(log + len + 1, buf_len - len - 1,
+		   "verifier wrote bytes past NULL termination\n");
+
+	if (memcmp(full_log, log, LOG_SIZE)) {
+		err("log did not match expected output\n");
+		exit(1);
+	}
+}
+
+static void test_log_bad(char *log, size_t log_len, int log_level)
+{
+	int ret;
+
+	ret = load(log, log_len, log_level);
+	check_ret(ret, EINVAL);
+	if (log)
+		check_ones(log, LOG_SIZE,
+			   "verifier touched log with bad parameters\n");
+}
+
+int main(int argc, char **argv)
+{
+	char full_log[LOG_SIZE];
+	char log[LOG_SIZE];
+	size_t want_len;
+	int i;
+
+	memset(log, 1, LOG_SIZE);
+
+	/* Test incorrect attr */
+	printf("Test log_level 0...\n");
+	test_log_bad(log, LOG_SIZE, 0);
+
+	printf("Test log_size < 128...\n");
+	test_log_bad(log, 15, 1);
+
+	printf("Test log_buff = NULL...\n");
+	test_log_bad(NULL, LOG_SIZE, 1);
+
+	/* Test with log big enough */
+	printf("Test oversized buffer...\n");
+	test_log_good(full_log, LOG_SIZE, LOG_SIZE, 0, EACCES, full_log);
+
+	want_len = strlen(full_log);
+
+	printf("Test exact buffer...\n");
+	test_log_good(log, LOG_SIZE, want_len + 2, want_len, EACCES, full_log);
+
+	printf("Test undersized buffers...\n");
+	for (i = 0; i < 64; i++) {
+		full_log[want_len - i + 1] = 1;
+		full_log[want_len - i] = 0;
+
+		test_log_good(log, LOG_SIZE, want_len + 1 - i, want_len - i,
+			      ENOSPC, full_log);
+	}
+
+	printf("test_verifier_log: OK\n");
+	return 0;
+}