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bpf: selftests: Add helpers to directly use the capget and capset syscall

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After upgrading to the newer libcap (>= 2.60),
the libcap commit aca076443591 ("Make cap_t operations thread safe.")
added a "__u8 mutex;" to the "struct _cap_struct".  It caused a few byte
shift that breaks the assumption made in the "struct libcap" definition
in test_verifier.c.

The bpf selftest usage only needs to enable and disable the effective
caps of the running task.  It is easier to directly syscall the
capget and capset instead.  It can also remove the libcap
library dependency.

The cap_helpers.{c,h} is added.  One __u64 is used for all CAP_*
bits instead of two __u32.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20220316173823.2036955-1-kafai@fb.com
This commit is contained in:
Martin KaFai Lau 2022-03-16 10:38:23 -07:00 committed by Alexei Starovoitov
parent 6585abea98
commit 663af70aab
2 changed files with 86 additions and 0 deletions
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67
tools/testing/selftests/bpf/cap_helpers.c Normal file
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// SPDX-License-Identifier: GPL-2.0
#include "cap_helpers.h"
/* Avoid including <sys/capability.h> from the libcap-devel package,
* so directly declare them here and use them from glibc.
*/
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);
int cap_enable_effective(__u64 caps, __u64 *old_caps)
{
struct __user_cap_data_struct data[_LINUX_CAPABILITY_U32S_3];
struct __user_cap_header_struct hdr = {
.version = _LINUX_CAPABILITY_VERSION_3,
};
__u32 cap0 = caps;
__u32 cap1 = caps >> 32;
int err;
err = capget(&hdr, data);
if (err)
return err;
if (old_caps)
*old_caps = (__u64)(data[1].effective) << 32 | data[0].effective;
if ((data[0].effective & cap0) == cap0 &&
(data[1].effective & cap1) == cap1)
return 0;
data[0].effective |= cap0;
data[1].effective |= cap1;
err = capset(&hdr, data);
if (err)
return err;
return 0;
}
int cap_disable_effective(__u64 caps, __u64 *old_caps)
{
struct __user_cap_data_struct data[_LINUX_CAPABILITY_U32S_3];
struct __user_cap_header_struct hdr = {
.version = _LINUX_CAPABILITY_VERSION_3,
};
__u32 cap0 = caps;
__u32 cap1 = caps >> 32;
int err;
err = capget(&hdr, data);
if (err)
return err;
if (old_caps)
*old_caps = (__u64)(data[1].effective) << 32 | data[0].effective;
if (!(data[0].effective & cap0) && !(data[1].effective & cap1))
return 0;
data[0].effective &= ~cap0;
data[1].effective &= ~cap1;
err = capset(&hdr, data);
if (err)
return err;
return 0;
}

19
tools/testing/selftests/bpf/cap_helpers.h Normal file
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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __CAP_HELPERS_H
#define __CAP_HELPERS_H
#include <linux/types.h>
#include <linux/capability.h>
#ifndef CAP_PERFMON
#define CAP_PERFMON 38
#endif
#ifndef CAP_BPF
#define CAP_BPF 39
#endif
int cap_enable_effective(__u64 caps, __u64 *old_caps);
int cap_disable_effective(__u64 caps, __u64 *old_caps);
#endif