[PATCH v2 bpf-next 0/3] Remove libcap dependency from bpf selftests

[PATCH v2 bpf-next 0/3] Remove libcap dependency from bpf selftests

[Martin KaFai Lau]

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)

Martin KaFai Lau (3):
  bpf: selftests: Add helpers to directly use the capget and capset
    syscall
  bpf: selftests: Remove libcap usage from test_verifier
  bpf: selftests: Remove libcap usage from test_progs

 tools/testing/selftests/bpf/Makefile          |  8 +-
 tools/testing/selftests/bpf/cap_helpers.c     | 67 ++++++++++++++
 tools/testing/selftests/bpf/cap_helpers.h     | 19 ++++
 .../selftests/bpf/prog_tests/bind_perm.c      | 44 ++--------
 tools/testing/selftests/bpf/test_verifier.c   | 88 ++++++-------------
 5 files changed, 124 insertions(+), 102 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/cap_helpers.c
 create mode 100644 tools/testing/selftests/bpf/cap_helpers.h

-- 
2.30.2

[PATCH v2 bpf-next 1/3] bpf: selftests: Add helpers to directly use the capget and capset syscall

[Martin KaFai Lau]

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.

The bpf selftest usage only needs to enable and disable the effective
caps of the running task.  It is easier to directly syscall the
capget and capset instead.  It can also remove the libcap
library dependency.

The cap_helpers.{c,h} is added.  One __u64 is used for all CAP_*
bits instead of two __u32.

Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
 tools/testing/selftests/bpf/cap_helpers.c | 67 +++++++++++++++++++++++
 tools/testing/selftests/bpf/cap_helpers.h | 19 +++++++
 2 files changed, 86 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/cap_helpers.c
 create mode 100644 tools/testing/selftests/bpf/cap_helpers.h

diff --git a/tools/testing/selftests/bpf/cap_helpers.c b/tools/testing/selftests/bpf/cap_helpers.c
new file mode 100644
index 000000000000..d5ac507401d7
--- /dev/null
+++ b/tools/testing/selftests/bpf/cap_helpers.c
@@ -0,0 +1,67 @@
+// 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;
+}
diff --git a/tools/testing/selftests/bpf/cap_helpers.h b/tools/testing/selftests/bpf/cap_helpers.h
new file mode 100644
index 000000000000..6d163530cb0f
--- /dev/null
+++ b/tools/testing/selftests/bpf/cap_helpers.h
@@ -0,0 +1,19 @@
+/* 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
-- 
2.30.2

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

[Martin KaFai Lau]

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 <john.fastabend@gmail.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
 tools/testing/selftests/bpf/Makefile        |  3 +-
 tools/testing/selftests/bpf/test_verifier.c | 88 ++++++---------------
 2 files changed, 27 insertions(+), 64 deletions(-)

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()
-- 
2.30.2

[PATCH v2 bpf-next 3/3] bpf: selftests: Remove libcap usage from test_progs

[Martin KaFai Lau]

This patch removes the libcap usage from test_progs.
bind_perm.c is the only user.  cap_*_effective() helpers added in the
earlier patch are directly used instead.

No other selftest binary is using libcap, so '-lcap' is also removed
from the Makefile.

Acked-by: John Fastabend <john.fastabend@gmail.com>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
 tools/testing/selftests/bpf/Makefile          |  5 ++-
 .../selftests/bpf/prog_tests/bind_perm.c      | 44 ++++---------------
 2 files changed, 11 insertions(+), 38 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 1c6e55740019..11f5883636c3 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -25,7 +25,7 @@ CFLAGS += -g -O0 -rdynamic -Wall -Werror $(GENFLAGS) $(SAN_CFLAGS)	\
 	  -I$(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),)
@@ -480,7 +480,8 @@ TRUNNER_TESTS_DIR := prog_tests
 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)
diff --git a/tools/testing/selftests/bpf/prog_tests/bind_perm.c b/tools/testing/selftests/bpf/prog_tests/bind_perm.c
index eac71fbb24ce..a1766a298bb7 100644
--- a/tools/testing/selftests/bpf/prog_tests/bind_perm.c
+++ b/tools/testing/selftests/bpf/prog_tests/bind_perm.c
@@ -4,9 +4,9 @@
 #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;
@@ -49,41 +49,11 @@ void try_bind(int family, int port, int expected_errno)
 		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())
@@ -105,7 +75,8 @@ void test_bind_perm(void)
 	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);
@@ -113,8 +84,9 @@ void test_bind_perm(void)
 	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);
-- 
2.30.2

Re: [PATCH v2 bpf-next 0/3] Remove libcap dependency from bpf selftests

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Wed, 16 Mar 2022 10:38:16 -0700 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [v2,bpf-next,1/3] bpf: selftests: Add helpers to directly use the capget and capset syscall
    https://git.kernel.org/bpf/bpf-next/c/663af70aabb7
  - [v2,bpf-next,2/3] bpf: selftests: Remove libcap usage from test_verifier
    https://git.kernel.org/bpf/bpf-next/c/b1c2768a82b9
  - [v2,bpf-next,3/3] bpf: selftests: Remove libcap usage from test_progs
    https://git.kernel.org/bpf/bpf-next/c/82cb2b30773e

You are awesome, thank you!
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