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Message-ID: <a2ab9671-5095-47bf-82cf-0e167320772f@163.com>
Date: Fri, 11 Oct 2024 14:59:08 +0800
From: zhouyuhang <zhouyuhang1010@....com>
To: Shuah Khan <skhan@...uxfoundation.org>, brauner@...nel.org,
shuah@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
zhouyuhang <zhouyuhang@...inos.cn>
Subject: Re: [PATCH] selftests: clone3: Use the capget and capset syscall
directly
On 2024/10/10 23:50, Shuah Khan wrote:
> On 10/10/24 06:16, zhouyuhang wrote:
>> 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.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.
>
Thanks, I'll fix it in V2
>> Signed-off-by: zhouyuhang <zhouyuhang@...inos.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.
>
I tested it on my machine without libcap-dev installed, the
/usr/include/linux/capability.h
is on this machine by default. Successfully compiled using #include
<linux/capability.h>
but not with #include <sys/capability.h>. This patch removes libcap
library dependencies.
And we don't use any part of sys/capability.h other than these two
syscalls. So I think that's why it's necessary.
>> +
>> 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
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