From: zhouyuhang <zhouyuhang@kylinos.cn>

The libcap commit aca076443591 ("Make cap_t operations thread safe.")
added a __u8 mutex at the beginning of the struct _cap_struct, it changes
the offset of the members in the structure that breaks the assumption
made in the "struct libcap" definition in clone3_cap_checkpoint_restore.c.
This causes the call to cap_set_proc here to fail with error code EPERM,
and the output is as follows:

 #  RUN           global.clone3_cap_checkpoint_restore ...
 # clone3() syscall supported
 # clone3_cap_checkpoint_restore.c:151:clone3_cap_checkpoint_restore:Child has PID 130508
 cap_set_proc: Operation not permitted
 # clone3_cap_checkpoint_restore.c:160:clone3_cap_checkpoint_restore:Expected set_capability() (-1) == 0 (0)
 # clone3_cap_checkpoint_restore.c:161:clone3_cap_checkpoint_restore:Could not set CAP_CHECKPOINT_RESTORE
 # clone3_cap_checkpoint_restore: Test terminated by assertion
 #          FAIL  global.clone3_cap_checkpoint_restore

Changing to using capget and capset syscall directly here can fix this error,
just like what the commit 663af70aabb7 ("bpf: selftests: Add helpers to directly
use the capget and capset syscall") does.
The output is as follows:

 #  RUN           global.clone3_cap_checkpoint_restore ...
 # clone3() syscall supported
 # clone3_cap_checkpoint_restore.c:160:clone3_cap_checkpoint_restore:Child has PID 23708
 # clone3_cap_checkpoint_restore.c:91:clone3_cap_checkpoint_restore:[23707] Trying clone3() with CLONE_SET_TID to 23708
 # clone3_cap_checkpoint_restore.c:58:clone3_cap_checkpoint_restore:Operation not permitted - Failed to create new process
 # clone3_cap_checkpoint_restore.c:93:clone3_cap_checkpoint_restore:[23707] clone3() with CLONE_SET_TID 23708 says:-1
 # clone3_cap_checkpoint_restore.c:91:clone3_cap_checkpoint_restore:[23707] Trying clone3() with CLONE_SET_TID to 23708
 # clone3_cap_checkpoint_restore.c:73:clone3_cap_checkpoint_restore:I am the parent (23707). My child's pid is 23708
 # clone3_cap_checkpoint_restore.c:66:clone3_cap_checkpoint_restore:I am the child, my PID is 23708 (expected 23708)
 # clone3_cap_checkpoint_restore.c:93:clone3_cap_checkpoint_restore:[23707] clone3() with CLONE_SET_TID 23708 says:0
 #            OK  global.clone3_cap_checkpoint_restore
 ok 1 global.clone3_cap_checkpoint_restore
 # PASSED: 1 / 1 tests passed.

Signed-off-by: zhouyuhang <zhouyuhang@kylinos.cn>
---
v4:
	* Add some comments and modify the output and return value when set_capability fails
v3:
	* Remove locally declared system calls and retained the - lcap in the Makefile.
v2:
	* Move locally declared system calls to header file.
v1:
	* Directly using capget and capset and declare them locally.
---
 .../clone3/clone3_cap_checkpoint_restore.c    | 77 +++++++++++--------
 1 file changed, 43 insertions(+), 34 deletions(-)

diff --git a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
index 3c196fa86c99..076f9d4cce60 100644
--- a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
+++ b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
@@ -27,6 +27,13 @@
 #include "../kselftest_harness.h"
 #include "clone3_selftests.h"
 
+/*
+ * Prevent not being defined in the header file
+ */
+#ifndef CAP_CHECKPOINT_RESTORE
+#define CAP_CHECKPOINT_RESTORE 40
+#endif
+
 static void child_exit(int ret)
 {
 	fflush(stdout);
@@ -87,47 +94,49 @@ static int test_clone3_set_tid(struct __test_metadata *_metadata,
 	return ret;
 }
 
-struct libcap {
-	struct __user_cap_header_struct hdr;
+static int set_capability(struct __test_metadata *_metadata)
+{
 	struct __user_cap_data_struct data[2];
-};
 
-static int set_capability(void)
-{
-	cap_value_t cap_values[] = { CAP_SETUID, CAP_SETGID };
-	struct libcap *cap;
-	int ret = -1;
-	cap_t caps;
-
-	caps = cap_get_proc();
-	if (!caps) {
-		perror("cap_get_proc");
-		return -1;
-	}
+	/*
+	 * Only _LINUX_CAPABILITY_VERSION_3 can be used here.
+	 * _LINUX_CAPABILITY_VERSION_1 represents use 32-bit capabilities,
+	 * using it will cause CAP_CHECKPOINT_RESTORE to not be set.
+	 * _LINUX_CAPABILITY_VERSION_2 has already been deprecated.
+	 */
+	struct __user_cap_header_struct hdr = {
+		.version = _LINUX_CAPABILITY_VERSION_3,
+	};
 
-	/* Drop all capabilities */
-	if (cap_clear(caps)) {
-		perror("cap_clear");
-		goto out;
+	/*
+	 * CAP_CHECKPOINT_RESTORE is greater than 31, so we need two u32.
+	 * cap0 is the lower 32bit and cap1 is the higher 32bit, they will
+	 * be combined into a u64 in mk_kernel_cap.
+	 */
+	__u32 cap0 = 1 << CAP_SETUID | 1 << CAP_SETGID;
+	__u32 cap1 = 1 << (CAP_CHECKPOINT_RESTORE - 32);
+	int ret;
+
+	ret = capget(&hdr, data);
+	if (ret) {
+		TH_LOG("%s - Failed to get capability", strerror(errno));
+		return -errno;
 	}
 
-	cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_values, CAP_SET);
-	cap_set_flag(caps, CAP_PERMITTED, 2, cap_values, CAP_SET);
+	/* Drop all capabilities */
+	memset(&data, 0, sizeof(data));
 
-	cap = (struct libcap *) caps;
+	data[0].effective |= cap0;
+	data[0].permitted |= cap0;
 
-	/* 40 -> CAP_CHECKPOINT_RESTORE */
-	cap->data[1].effective |= 1 << (40 - 32);
-	cap->data[1].permitted |= 1 << (40 - 32);
+	data[1].effective |= cap1;
+	data[1].permitted |= cap1;
 
-	if (cap_set_proc(caps)) {
-		perror("cap_set_proc");
-		goto out;
+	ret = capset(&hdr, data);
+	if (ret) {
+		TH_LOG("%s - Failed to set capability", strerror(errno));
+		return -errno;
 	}
-	ret = 0;
-out:
-	if (cap_free(caps))
-		perror("cap_free");
 	return ret;
 }
 
@@ -157,7 +166,7 @@ TEST(clone3_cap_checkpoint_restore)
 	/* After the child has finished, its PID should be free. */
 	set_tid[0] = pid;
 
-	ASSERT_EQ(set_capability(), 0)
+	ASSERT_EQ(set_capability(_metadata), 0)
 		TH_LOG("Could not set CAP_CHECKPOINT_RESTORE");
 
 	ASSERT_EQ(prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0), 0);
@@ -169,7 +178,7 @@ TEST(clone3_cap_checkpoint_restore)
 	set_tid[0] = pid;
 	/* This would fail without CAP_CHECKPOINT_RESTORE */
 	ASSERT_EQ(test_clone3_set_tid(_metadata, set_tid, 1), -EPERM);
-	ASSERT_EQ(set_capability(), 0)
+	ASSERT_EQ(set_capability(_metadata), 0)
 		TH_LOG("Could not set CAP_CHECKPOINT_RESTORE");
 	/* This should work as we have CAP_CHECKPOINT_RESTORE as non-root */
 	ASSERT_EQ(test_clone3_set_tid(_metadata, set_tid, 1), 0);
-- 
2.27.0