Merge branch 'Remove libcap dependency from bpf selftests'

Martin KaFai Lau says:

====================

After upgrading to the newer libcap (>= 2.60),
the libcap commit aca076443591 ("Make cap_t operations thread safe.")
added a "__u8 mutex;" to the "struct _cap_struct". It caused a few byte
shift that breaks the assumption made in the "struct libcap" definition
in test_verifier.c.

This set is to remove the libcap dependency from the bpf selftests.

v2:
- Define CAP_PERFMON and CAP_BPF when the older <linux/capability.h>
does not have them. (Andrii)
====================

Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/testing/selftests/bpf/Makefile

···
 	  -I$(CURDIR) -I$(INCLUDE_DIR) -I$(GENDIR) -I$(LIBDIR)		\
 	  -I$(TOOLSINCDIR) -I$(APIDIR) -I$(OUTPUT)
 LDFLAGS += $(SAN_CFLAGS)
-LDLIBS += -lcap -lelf -lz -lrt -lpthread
+LDLIBS += -lelf -lz -lrt -lpthread
 
 # Silence some warnings when compiled with clang
 ifneq ($(LLVM),)
···
 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)
···
 $(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)    \
···
 TRUNNER_BPF_PROGS_DIR := progs
 TRUNNER_EXTRA_SOURCES := test_progs.c cgroup_helpers.c trace_helpers.c	\
 			 network_helpers.c testing_helpers.c		\
-			 btf_helpers.c flow_dissector_load.h
+			 btf_helpers.c flow_dissector_load.h		\
+			 cap_helpers.c
 TRUNNER_EXTRA_FILES := $(OUTPUT)/urandom_read $(OUTPUT)/bpf_testmod.ko	\
 		       ima_setup.sh					\
 		       $(wildcard progs/btf_dump_test_case_*.c)

tools/testing/selftests/bpf/cap_helpers.c

···
+// SPDX-License-Identifier: GPL-2.0
+#include "cap_helpers.h"
+
+/* Avoid including <sys/capability.h> from the libcap-devel package,
+ * so directly declare them here and use them from glibc.
+ */
+int capget(cap_user_header_t header, cap_user_data_t data);
+int capset(cap_user_header_t header, const cap_user_data_t data);
+
+int cap_enable_effective(__u64 caps, __u64 *old_caps)
+{
+	struct __user_cap_data_struct data[_LINUX_CAPABILITY_U32S_3];
+	struct __user_cap_header_struct hdr = {
+		.version = _LINUX_CAPABILITY_VERSION_3,
+	};
+	__u32 cap0 = caps;
+	__u32 cap1 = caps >> 32;
+	int err;
+
+	err = capget(&hdr, data);
+	if (err)
+		return err;
+
+	if (old_caps)
+		*old_caps = (__u64)(data[1].effective) << 32 | data[0].effective;
+
+	if ((data[0].effective & cap0) == cap0 &&
+	    (data[1].effective & cap1) == cap1)
+		return 0;
+
+	data[0].effective |= cap0;
+	data[1].effective |= cap1;
+	err = capset(&hdr, data);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+int cap_disable_effective(__u64 caps, __u64 *old_caps)
+{
+	struct __user_cap_data_struct data[_LINUX_CAPABILITY_U32S_3];
+	struct __user_cap_header_struct hdr = {
+		.version = _LINUX_CAPABILITY_VERSION_3,
+	};
+	__u32 cap0 = caps;
+	__u32 cap1 = caps >> 32;
+	int err;
+
+	err = capget(&hdr, data);
+	if (err)
+		return err;
+
+	if (old_caps)
+		*old_caps = (__u64)(data[1].effective) << 32 | data[0].effective;
+
+	if (!(data[0].effective & cap0) && !(data[1].effective & cap1))
+		return 0;
+
+	data[0].effective &= ~cap0;
+	data[1].effective &= ~cap1;
+	err = capset(&hdr, data);
+	if (err)
+		return err;
+
+	return 0;
+}

tools/testing/selftests/bpf/cap_helpers.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __CAP_HELPERS_H
+#define __CAP_HELPERS_H
+
+#include <linux/types.h>
+#include <linux/capability.h>
+
+#ifndef CAP_PERFMON
+#define CAP_PERFMON		38
+#endif
+
+#ifndef CAP_BPF
+#define CAP_BPF			39
+#endif
+
+int cap_enable_effective(__u64 caps, __u64 *old_caps);
+int cap_disable_effective(__u64 caps, __u64 *old_caps);
+
+#endif

tools/testing/selftests/bpf/prog_tests/bind_perm.c

···
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/socket.h>
-#include <sys/capability.h>
 
 #include "test_progs.h"
+#include "cap_helpers.h"
 #include "bind_perm.skel.h"
 
 static int duration;
···
 		close(fd);
 }
 
-bool cap_net_bind_service(cap_flag_value_t flag)
-{
-	const cap_value_t cap_net_bind_service = CAP_NET_BIND_SERVICE;
-	cap_flag_value_t original_value;
-	bool was_effective = false;
-	cap_t caps;
-
-	caps = cap_get_proc();
-	if (CHECK(!caps, "cap_get_proc", "errno %d", errno))
-		goto free_caps;
-
-	if (CHECK(cap_get_flag(caps, CAP_NET_BIND_SERVICE, CAP_EFFECTIVE,
-			       &original_value),
-		  "cap_get_flag", "errno %d", errno))
-		goto free_caps;
-
-	was_effective = (original_value == CAP_SET);
-
-	if (CHECK(cap_set_flag(caps, CAP_EFFECTIVE, 1, &cap_net_bind_service,
-			       flag),
-		  "cap_set_flag", "errno %d", errno))
-		goto free_caps;
-
-	if (CHECK(cap_set_proc(caps), "cap_set_proc", "errno %d", errno))
-		goto free_caps;
-
-free_caps:
-	CHECK(cap_free(caps), "cap_free", "errno %d", errno);
-	return was_effective;
-}
-
 void test_bind_perm(void)
 {
-	bool cap_was_effective;
+	const __u64 net_bind_svc_cap = 1ULL << CAP_NET_BIND_SERVICE;
 	struct bind_perm *skel;
+	__u64 old_caps = 0;
 	int cgroup_fd;
 
 	if (create_netns())
···
 	if (!ASSERT_OK_PTR(skel, "bind_v6_prog"))
 		goto close_skeleton;
 
-	cap_was_effective = cap_net_bind_service(CAP_CLEAR);
+	ASSERT_OK(cap_disable_effective(net_bind_svc_cap, &old_caps),
+		  "cap_disable_effective");
 
 	try_bind(AF_INET, 110, EACCES);
 	try_bind(AF_INET6, 110, EACCES);
···
 	try_bind(AF_INET, 111, 0);
 	try_bind(AF_INET6, 111, 0);
 
-	if (cap_was_effective)
-		cap_net_bind_service(CAP_SET);
+	if (old_caps & net_bind_svc_cap)
+		ASSERT_OK(cap_enable_effective(net_bind_svc_cap, NULL),
+			  "cap_enable_effective");
 
 close_skeleton:
 	bind_perm__destroy(skel);

tools/testing/selftests/bpf/test_verifier.c

···
 #include <limits.h>
 #include <assert.h>
 
-#include <sys/capability.h>
-
 #include <linux/unistd.h>
 #include <linux/filter.h>
 #include <linux/bpf_perf_event.h>
···
 #  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"
···
 #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;
···
 
 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;
+	int err;
 
-	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
-	 */
 	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));
+		err = cap_disable_effective(ADMIN_CAPS, NULL);
+		if (err)
+			perror("cap_disable_effective(ADMIN_CAPS)");
 	}
-	if (cap_set_proc(caps)) {
-		perror("cap_set_proc");
-		goto out;
-	}
-	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,
···
 
 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;
+	__u64 caps;
 
-#ifdef CAP_IS_SUPPORTED
-	if (!CAP_IS_SUPPORTED(CAP_SETFCAP)) {
-		perror("cap_get_flag");
+	/* 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;
 	}
-#endif
-	caps = cap_get_proc();
-	if (!caps) {
-		perror("cap_get_proc");
-		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()