[v2,bpf-next,2/3] bpf: selftests: Remove libcap usage from test_verifier

Commit Message

Martin KaFai Lau March 16, 2022, 5:38 p.m. UTC

This patch removes the libcap usage from test_verifier.
The cap_*_effective() helpers added in the earlier patch are
used instead.

Acked-by: John Fastabend <[e-mail]>
Signed-off-by: Martin KaFai Lau <[e-mail]>
---
 tools/testing/selftests/bpf/Makefile        |  3 +-
 tools/testing/selftests/bpf/test_verifier.c | 88 ++++++---------------
 2 files changed, 27 insertions(+), 64 deletions(-)

Patch

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index fe12b4f5fe20..1c6e55740019 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -195,6 +195,7 @@  $(TEST_GEN_PROGS) $(TEST_GEN_PROGS_EXTENDED): $(BPFOBJ)
 CGROUP_HELPERS	:= $(OUTPUT)/cgroup_helpers.o
 TESTING_HELPERS	:= $(OUTPUT)/testing_helpers.o
 TRACE_HELPERS	:= $(OUTPUT)/trace_helpers.o
+CAP_HELPERS	:= $(OUTPUT)/cap_helpers.o
 
 $(OUTPUT)/test_dev_cgroup: $(CGROUP_HELPERS) $(TESTING_HELPERS)
 $(OUTPUT)/test_skb_cgroup_id_user: $(CGROUP_HELPERS) $(TESTING_HELPERS)
@@ -211,7 +212,7 @@  $(OUTPUT)/test_lirc_mode2_user: $(TESTING_HELPERS)
 $(OUTPUT)/xdping: $(TESTING_HELPERS)
 $(OUTPUT)/flow_dissector_load: $(TESTING_HELPERS)
 $(OUTPUT)/test_maps: $(TESTING_HELPERS)
-$(OUTPUT)/test_verifier: $(TESTING_HELPERS)
+$(OUTPUT)/test_verifier: $(TESTING_HELPERS) $(CAP_HELPERS)
 
 BPFTOOL ?= $(DEFAULT_BPFTOOL)
 $(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)    \
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 92e3465fbae8..a2cd236c32eb 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -22,8 +22,6 @@ 
 #include <limits.h>
 #include <assert.h>
 
-#include <sys/capability.h>
-
 #include <linux/unistd.h>
 #include <linux/filter.h>
 #include <linux/bpf_perf_event.h>
@@ -42,6 +40,7 @@ 
 #  define CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS 1
 # endif
 #endif
+#include "cap_helpers.h"
 #include "bpf_rand.h"
 #include "bpf_util.h"
 #include "test_btf.h"
@@ -62,6 +61,10 @@ 
 #define F_NEEDS_EFFICIENT_UNALIGNED_ACCESS	(1 << 0)
 #define F_LOAD_WITH_STRICT_ALIGNMENT		(1 << 1)
 
+/* need CAP_BPF, CAP_NET_ADMIN, CAP_PERFMON to load progs */
+#define ADMIN_CAPS (1ULL << CAP_NET_ADMIN |	\
+		    1ULL << CAP_PERFMON |	\
+		    1ULL << CAP_BPF)
 #define UNPRIV_SYSCTL "kernel/unprivileged_bpf_disabled"
 static bool unpriv_disabled = false;
 static int skips;
@@ -973,47 +976,19 @@  struct libcap {
 
 static int set_admin(bool admin)
 {
-	cap_t caps;
-	/* need CAP_BPF, CAP_NET_ADMIN, CAP_PERFMON to load progs */
-	const cap_value_t cap_net_admin = CAP_NET_ADMIN;
-	const cap_value_t cap_sys_admin = CAP_SYS_ADMIN;
-	struct libcap *cap;
-	int ret = -1;
-
-	caps = cap_get_proc();
-	if (!caps) {
-		perror("cap_get_proc");
-		return -1;
-	}
-	cap = (struct libcap *)caps;
-	if (cap_set_flag(caps, CAP_EFFECTIVE, 1, &cap_sys_admin, CAP_CLEAR)) {
-		perror("cap_set_flag clear admin");
-		goto out;
-	}
-	if (cap_set_flag(caps, CAP_EFFECTIVE, 1, &cap_net_admin,
-				admin ? CAP_SET : CAP_CLEAR)) {
-		perror("cap_set_flag set_or_clear net");
-		goto out;
-	}
-	/* libcap is likely old and simply ignores CAP_BPF and CAP_PERFMON,
-	 * so update effective bits manually
-	 */
+	int err;
+
 	if (admin) {
-		cap->data[1].effective |= 1 << (38 /* CAP_PERFMON */ - 32);
-		cap->data[1].effective |= 1 << (39 /* CAP_BPF */ - 32);
+		err = cap_enable_effective(ADMIN_CAPS, NULL);
+		if (err)
+			perror("cap_enable_effective(ADMIN_CAPS)");
 	} else {
-		cap->data[1].effective &= ~(1 << (38 - 32));
-		cap->data[1].effective &= ~(1 << (39 - 32));
-	}
-	if (cap_set_proc(caps)) {
-		perror("cap_set_proc");
-		goto out;
+		err = cap_disable_effective(ADMIN_CAPS, NULL);
+		if (err)
+			perror("cap_disable_effective(ADMIN_CAPS)");
 	}
-	ret = 0;
-out:
-	if (cap_free(caps))
-		perror("cap_free");
-	return ret;
+
+	return err;
 }
 
 static int do_prog_test_run(int fd_prog, bool unpriv, uint32_t expected_val,
@@ -1291,31 +1266,18 @@  static void do_test_single(struct bpf_test *test, bool unpriv,
 
 static bool is_admin(void)
 {
-	cap_flag_value_t net_priv = CAP_CLEAR;
-	bool perfmon_priv = false;
-	bool bpf_priv = false;
-	struct libcap *cap;
-	cap_t caps;
-
-#ifdef CAP_IS_SUPPORTED
-	if (!CAP_IS_SUPPORTED(CAP_SETFCAP)) {
-		perror("cap_get_flag");
-		return false;
-	}
-#endif
-	caps = cap_get_proc();
-	if (!caps) {
-		perror("cap_get_proc");
+	__u64 caps;
+
+	/* The test checks for finer cap as CAP_NET_ADMIN,
+	 * CAP_PERFMON, and CAP_BPF instead of CAP_SYS_ADMIN.
+	 * Thus, disable CAP_SYS_ADMIN at the beginning.
+	 */
+	if (cap_disable_effective(1ULL << CAP_SYS_ADMIN, &caps)) {
+		perror("cap_disable_effective(CAP_SYS_ADMIN)");
 		return false;
 	}
-	cap = (struct libcap *)caps;
-	bpf_priv = cap->data[1].effective & (1 << (39/* CAP_BPF */ - 32));
-	perfmon_priv = cap->data[1].effective & (1 << (38/* CAP_PERFMON */ - 32));
-	if (cap_get_flag(caps, CAP_NET_ADMIN, CAP_EFFECTIVE, &net_priv))
-		perror("cap_get_flag NET");
-	if (cap_free(caps))
-		perror("cap_free");
-	return bpf_priv && perfmon_priv && net_priv == CAP_SET;
+
+	return (caps & ADMIN_CAPS) == ADMIN_CAPS;
 }
 
 static void get_unpriv_disabled()