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Message-Id: <20241105062948.1037011-1-zhouyuhang1010@163.com>
Date: Tue, 5 Nov 2024 14:29:48 +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 v4] 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 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@...inos.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
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