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);