linux-kernel - [PATCH v3] selftests: clone3: Use the capget and capset syscall directly

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Message-Id: <20241030025045.1156941-1-zhouyuhang1010@163.com>
Date: Wed, 30 Oct 2024 10:50:45 +0800
From: zhouyuhang <zhouyuhang1010@....com>
To: brauner@...nel.org,
	shuah@...nel.org
Cc: linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	zhouyuhang <zhouyuhang@...inos.cn>
Subject: [PATCH v3] selftests: clone3: Use the capget and capset syscall directly

From: zhouyuhang <zhouyuhang@...inos.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 will cause the test case to fail with the following output:

 #  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.

Signed-off-by: zhouyuhang <zhouyuhang@...inos.cn>
---
 .../clone3/clone3_cap_checkpoint_restore.c    | 58 +++++++++----------
 1 file changed, 27 insertions(+), 31 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..8b61702bf721 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 +94,36 @@ static int test_clone3_set_tid(struct __test_metadata *_metadata,
 	return ret;
 }
 
-struct libcap {
-	struct __user_cap_header_struct hdr;
-	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");
+	struct __user_cap_data_struct data[2];
+	struct __user_cap_header_struct hdr = {
+		.version = _LINUX_CAPABILITY_VERSION_3,
+	};
+	__u32 cap0 = 1 << CAP_SETUID | 1 << CAP_SETGID;
+	__u32 cap1 = 1 << (CAP_CHECKPOINT_RESTORE - 32);
+	int ret;
+
+	ret = capget(&hdr, data);
+	if (ret) {
+		perror("capget");
 		return -1;
 	}
 
 	/* Drop all capabilities */
-	if (cap_clear(caps)) {
-		perror("cap_clear");
-		goto out;
-	}
-
-	cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_values, CAP_SET);
-	cap_set_flag(caps, CAP_PERMITTED, 2, cap_values, CAP_SET);
+	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) {
+		perror("capset");
+		return -1;
 	}
-	ret = 0;
-out:
-	if (cap_free(caps))
-		perror("cap_free");
 	return ret;
 }
 
-- 
2.27.0