Re: [PATCH] selftests: clone3: Use the capget and capset syscall directly

On 10/10/24 06:16, zhouyuhang wrote:

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.So use the capget and capset syscall directly and remove the libcap library dependency like the commit 663af70aabb7 ("bpf: selftests: Add helpers to directly use the capget and capset syscall") does.

NIT: grammar and comma spacing. Please fix those for readability. e.g: Change "struct _cap_struct,it" to "struct _cap_struct, it" Fix others as well.

Signed-off-by: zhouyuhang zhouyuhang@kylinos.cn

tools/testing/selftests/clone3/Makefile | 1 - .../clone3/clone3_cap_checkpoint_restore.c | 60 +++++++++---------- 2 files changed, 28 insertions(+), 33 deletions(-)

diff --git a/tools/testing/selftests/clone3/Makefile b/tools/testing/selftests/clone3/Makefile index 84832c369a2e..59d26e8da8d2 100644 --- a/tools/testing/selftests/clone3/Makefile +++ b/tools/testing/selftests/clone3/Makefile @@ -1,6 +1,5 @@ # SPDX-License-Identifier: GPL-2.0 CFLAGS += -g -std=gnu99 $(KHDR_INCLUDES) -LDLIBS += -lcap TEST_GEN_PROGS := clone3 clone3_clear_sighand clone3_set_tid \ clone3_cap_checkpoint_restore diff --git a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c index 3c196fa86c99..111912e2aead 100644 --- a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c +++ b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c @@ -15,7 +15,7 @@ #include <stdio.h> #include <stdlib.h> #include <stdbool.h> -#include <sys/capability.h> +#include <linux/capability.h> #include <sys/prctl.h> #include <sys/syscall.h> #include <sys/types.h> @@ -27,6 +27,13 @@ #include "../kselftest_harness.h" #include "clone3_selftests.h" +#ifndef CAP_CHECKPOINT_RESTORE +#define CAP_CHECKPOINT_RESTORE 40 +#endif

Why is this necessary? This is defined in linux/capability.h.

+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);

In general prototypes such as these should be defined in header file. Why are we defining these here?

These are defined in sys/capability.h

I don't understand this change. You are removing sys/capability.h which requires you to add these defines here. This doesn't sound like a correct solution to me.

• 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;
  

• }

• memset(&data, 0, sizeof(data));

• cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_values, CAP_SET);
• cap_set_flag(caps, CAP_PERMITTED, 2, cap_values, CAP_SET);

• data[0].effective |= cap0;
• data[0].permitted |= cap0;

• cap = (struct libcap *) caps;

• data[1].effective |= cap1;
• data[1].permitted |= cap1;

• /* 40 -> CAP_CHECKPOINT_RESTORE */
• cap->data[1].effective |= 1 << (40 - 32);
• cap->data[1].permitted |= 1 << (40 - 32);
• 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; }

thanks, -- Shuah