The LSM hook userns_create was introduced to provide LSM's an
opportunity to block or allow unprivileged user namespace creation. This
test serves two purposes: it provides a test eBPF implementation, and
tests the hook successfully blocks or allows user namespace creation.
This tests 4 cases:
1. Unattached bpf program does not block unpriv user namespace
creation.
2. Attached bpf program allows user namespace creation given
CAP_SYS_ADMIN privileges.
3. Attached bpf program denies user namespace creation for a
user without CAP_SYS_ADMIN.
4. The sleepable implementation loads
Signed-off-by: Frederick Lawler <[email protected]>
---
The generic deny_namespace file name is used for future namespace
expansion. I didn't want to limit these files to just the create_user_ns
hook.
Changes since v2:
- Rename create_user_ns hook to userns_create
Changes since v1:
- Introduce this patch
---
.../selftests/bpf/prog_tests/deny_namespace.c | 88 +++++++++++++++++++
.../selftests/bpf/progs/test_deny_namespace.c | 39 ++++++++
2 files changed, 127 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/deny_namespace.c
create mode 100644 tools/testing/selftests/bpf/progs/test_deny_namespace.c
diff --git a/tools/testing/selftests/bpf/prog_tests/deny_namespace.c b/tools/testing/selftests/bpf/prog_tests/deny_namespace.c
new file mode 100644
index 000000000000..9e4714295008
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/deny_namespace.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <test_progs.h>
+#include "test_deny_namespace.skel.h"
+#include <sched.h>
+#include "cap_helpers.h"
+
+#define STACK_SIZE (1024 * 1024)
+static char child_stack[STACK_SIZE];
+
+int clone_callback(void *arg)
+{
+ return 0;
+}
+
+static int create_new_user_ns(void)
+{
+ int status;
+ pid_t cpid;
+
+ cpid = clone(clone_callback, child_stack + STACK_SIZE,
+ CLONE_NEWUSER | SIGCHLD, NULL);
+
+ if (cpid == -1)
+ return errno;
+
+ if (cpid == 0)
+ return 0;
+
+ waitpid(cpid, &status, 0);
+ if (WIFEXITED(status))
+ return WEXITSTATUS(status);
+
+ return -1;
+}
+
+static void test_userns_create_bpf(void)
+{
+ __u32 cap_mask = 1ULL << CAP_SYS_ADMIN;
+ __u64 old_caps = 0;
+
+ ASSERT_OK(create_new_user_ns(), "priv new user ns");
+
+ cap_disable_effective(cap_mask, &old_caps);
+
+ ASSERT_EQ(create_new_user_ns(), EPERM, "unpriv new user ns");
+
+ if (cap_mask & old_caps)
+ cap_enable_effective(cap_mask, NULL);
+}
+
+static void test_unpriv_userns_create_no_bpf(void)
+{
+ __u32 cap_mask = 1ULL << CAP_SYS_ADMIN;
+ __u64 old_caps = 0;
+
+ cap_disable_effective(cap_mask, &old_caps);
+
+ ASSERT_OK(create_new_user_ns(), "no-bpf unpriv new user ns");
+
+ if (cap_mask & old_caps)
+ cap_enable_effective(cap_mask, NULL);
+}
+
+void test_deny_namespace(void)
+{
+ struct test_deny_namespace *skel = NULL;
+ int err;
+
+ if (test__start_subtest("unpriv_userns_create_no_bpf"))
+ test_unpriv_userns_create_no_bpf();
+
+ skel = test_deny_namespace__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "skel load"))
+ goto close_prog;
+
+ err = test_deny_namespace__attach(skel);
+ if (!ASSERT_OK(err, "attach"))
+ goto close_prog;
+
+ if (test__start_subtest("userns_create_bpf"))
+ test_userns_create_bpf();
+
+ test_deny_namespace__detach(skel);
+
+close_prog:
+ test_deny_namespace__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_deny_namespace.c b/tools/testing/selftests/bpf/progs/test_deny_namespace.c
new file mode 100644
index 000000000000..9ec9dabc8372
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_deny_namespace.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <errno.h>
+#include <linux/capability.h>
+
+struct kernel_cap_struct {
+ __u32 cap[_LINUX_CAPABILITY_U32S_3];
+} __attribute__((preserve_access_index));
+
+struct cred {
+ struct kernel_cap_struct cap_effective;
+} __attribute__((preserve_access_index));
+
+char _license[] SEC("license") = "GPL";
+
+SEC("lsm/userns_create")
+int BPF_PROG(test_userns_create, const struct cred *cred, int ret)
+{
+ struct kernel_cap_struct caps = cred->cap_effective;
+ int cap_index = CAP_TO_INDEX(CAP_SYS_ADMIN);
+ __u32 cap_mask = CAP_TO_MASK(CAP_SYS_ADMIN);
+
+ if (ret)
+ return 0;
+
+ ret = -EPERM;
+ if (caps.cap[cap_index] & cap_mask)
+ return 0;
+
+ return -EPERM;
+}
+
+SEC("lsm.s/userns_create")
+int BPF_PROG(test_sleepable_userns_create, const struct cred *cred, int ret)
+{
+ return 0;
+}
--
2.30.2
On Thu, Jul 21, 2022 at 12:28:07PM -0500, Frederick Lawler wrote:
> The LSM hook userns_create was introduced to provide LSM's an
> opportunity to block or allow unprivileged user namespace creation. This
> test serves two purposes: it provides a test eBPF implementation, and
> tests the hook successfully blocks or allows user namespace creation.
>
> This tests 4 cases:
>
> 1. Unattached bpf program does not block unpriv user namespace
> creation.
> 2. Attached bpf program allows user namespace creation given
> CAP_SYS_ADMIN privileges.
> 3. Attached bpf program denies user namespace creation for a
> user without CAP_SYS_ADMIN.
> 4. The sleepable implementation loads
>
> Signed-off-by: Frederick Lawler <[email protected]>
>
> ---
> The generic deny_namespace file name is used for future namespace
> expansion. I didn't want to limit these files to just the create_user_ns
> hook.
> Changes since v2:
> - Rename create_user_ns hook to userns_create
> Changes since v1:
> - Introduce this patch
> ---
> .../selftests/bpf/prog_tests/deny_namespace.c | 88 +++++++++++++++++++
> .../selftests/bpf/progs/test_deny_namespace.c | 39 ++++++++
> 2 files changed, 127 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/deny_namespace.c
> create mode 100644 tools/testing/selftests/bpf/progs/test_deny_namespace.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/deny_namespace.c b/tools/testing/selftests/bpf/prog_tests/deny_namespace.c
> new file mode 100644
> index 000000000000..9e4714295008
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/deny_namespace.c
> @@ -0,0 +1,88 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <test_progs.h>
> +#include "test_deny_namespace.skel.h"
> +#include <sched.h>
> +#include "cap_helpers.h"
> +
> +#define STACK_SIZE (1024 * 1024)
Does the child need 1M stack space ?
> +static char child_stack[STACK_SIZE];
> +
> +int clone_callback(void *arg)
static
> +{
> + return 0;
> +}
> +
> +static int create_new_user_ns(void)
> +{
> + int status;
> + pid_t cpid;
> +
> + cpid = clone(clone_callback, child_stack + STACK_SIZE,
> + CLONE_NEWUSER | SIGCHLD, NULL);
> +
> + if (cpid == -1)
> + return errno;
> +
> + if (cpid == 0)
Not an expert in clone() call and it is not clear what 0
return value mean from the man page. Could you explain ?
> + return 0;
> +
> + waitpid(cpid, &status, 0);
> + if (WIFEXITED(status))
> + return WEXITSTATUS(status);
> +
> + return -1;
> +}
> +
> +static void test_userns_create_bpf(void)
> +{
> + __u32 cap_mask = 1ULL << CAP_SYS_ADMIN;
> + __u64 old_caps = 0;
> +
> + ASSERT_OK(create_new_user_ns(), "priv new user ns");
Does it need to enable CAP_SYS_ADMIN first ?
> +
> + cap_disable_effective(cap_mask, &old_caps);
> +
> + ASSERT_EQ(create_new_user_ns(), EPERM, "unpriv new user ns");
> +
> + if (cap_mask & old_caps)
> + cap_enable_effective(cap_mask, NULL);
> +}
> +
> +static void test_unpriv_userns_create_no_bpf(void)
> +{
> + __u32 cap_mask = 1ULL << CAP_SYS_ADMIN;
> + __u64 old_caps = 0;
> +
> + cap_disable_effective(cap_mask, &old_caps);
> +
> + ASSERT_OK(create_new_user_ns(), "no-bpf unpriv new user ns");
> +
> + if (cap_mask & old_caps)
> + cap_enable_effective(cap_mask, NULL);
> +}
> +
> +void test_deny_namespace(void)
> +{
> + struct test_deny_namespace *skel = NULL;
> + int err;
> +
> + if (test__start_subtest("unpriv_userns_create_no_bpf"))
> + test_unpriv_userns_create_no_bpf();
> +
> + skel = test_deny_namespace__open_and_load();
> + if (!ASSERT_OK_PTR(skel, "skel load"))
> + goto close_prog;
> +
> + err = test_deny_namespace__attach(skel);
> + if (!ASSERT_OK(err, "attach"))
> + goto close_prog;
> +
> + if (test__start_subtest("userns_create_bpf"))
> + test_userns_create_bpf();
> +
> + test_deny_namespace__detach(skel);
> +
> +close_prog:
> + test_deny_namespace__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_deny_namespace.c b/tools/testing/selftests/bpf/progs/test_deny_namespace.c
> new file mode 100644
> index 000000000000..9ec9dabc8372
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_deny_namespace.c
> @@ -0,0 +1,39 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +#include <errno.h>
> +#include <linux/capability.h>
> +
> +struct kernel_cap_struct {
> + __u32 cap[_LINUX_CAPABILITY_U32S_3];
> +} __attribute__((preserve_access_index));
> +
> +struct cred {
> + struct kernel_cap_struct cap_effective;
> +} __attribute__((preserve_access_index));
> +
> +char _license[] SEC("license") = "GPL";
> +
> +SEC("lsm/userns_create")
> +int BPF_PROG(test_userns_create, const struct cred *cred, int ret)
> +{
> + struct kernel_cap_struct caps = cred->cap_effective;
> + int cap_index = CAP_TO_INDEX(CAP_SYS_ADMIN);
> + __u32 cap_mask = CAP_TO_MASK(CAP_SYS_ADMIN);
> +
> + if (ret)
> + return 0;
> +
> + ret = -EPERM;
> + if (caps.cap[cap_index] & cap_mask)
> + return 0;
> +
> + return -EPERM;
> +}
> +
> +SEC("lsm.s/userns_create")
> +int BPF_PROG(test_sleepable_userns_create, const struct cred *cred, int ret)
> +{
An empty program is weird. If the intention is
to ensure a sleepable program can attach to userns_create,
move the test logic here and remove the non-sleepable
program above.
> + return 0;
> +}
> --
> 2.30.2
>
On Thu, Jul 21, 2022 at 12:28:07PM -0500, Frederick Lawler wrote:
> The LSM hook userns_create was introduced to provide LSM's an
> opportunity to block or allow unprivileged user namespace creation. This
> test serves two purposes: it provides a test eBPF implementation, and
> tests the hook successfully blocks or allows user namespace creation.
>
> This tests 4 cases:
>
> 1. Unattached bpf program does not block unpriv user namespace
> creation.
> 2. Attached bpf program allows user namespace creation given
> CAP_SYS_ADMIN privileges.
> 3. Attached bpf program denies user namespace creation for a
> user without CAP_SYS_ADMIN.
> 4. The sleepable implementation loads
Sounds good!
>
> Signed-off-by: Frederick Lawler <[email protected]>
>
> ---
> The generic deny_namespace file name is used for future namespace
> expansion. I didn't want to limit these files to just the create_user_ns
> hook.
> Changes since v2:
> - Rename create_user_ns hook to userns_create
> Changes since v1:
> - Introduce this patch
> ---
> .../selftests/bpf/prog_tests/deny_namespace.c | 88 +++++++++++++++++++
> .../selftests/bpf/progs/test_deny_namespace.c | 39 ++++++++
> 2 files changed, 127 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/deny_namespace.c
> create mode 100644 tools/testing/selftests/bpf/progs/test_deny_namespace.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/deny_namespace.c b/tools/testing/selftests/bpf/prog_tests/deny_namespace.c
> new file mode 100644
> index 000000000000..9e4714295008
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/deny_namespace.c
> @@ -0,0 +1,88 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <test_progs.h>
> +#include "test_deny_namespace.skel.h"
> +#include <sched.h>
> +#include "cap_helpers.h"
> +
> +#define STACK_SIZE (1024 * 1024)
> +static char child_stack[STACK_SIZE];
> +
> +int clone_callback(void *arg)
> +{
> + return 0;
> +}
> +
> +static int create_new_user_ns(void)
> +{
> + int status;
> + pid_t cpid;
> +
> + cpid = clone(clone_callback, child_stack + STACK_SIZE,
> + CLONE_NEWUSER | SIGCHLD, NULL);
> +
> + if (cpid == -1)
> + return errno;
> +
> + if (cpid == 0)
> + return 0;
Martin asked about this already but fwiw, this cannot happen with
clone(). The clone() function doesn't return twice. It always returns
the PID of the child process or an error.
> +
> + waitpid(cpid, &status, 0);
> + if (WIFEXITED(status))
> + return WEXITSTATUS(status);
> +
> + return -1;
> +}
You can also just avoid the clone() dance and simply do sm like:
static int wait_for_pid(pid_t pid)
{
int status, ret;
again:
ret = waitpid(pid, &status, 0);
if (ret == -1) {
if (errno == EINTR)
goto again;
return -1;
}
if (!WIFEXITED(status))
return -1;
return WEXITSTATUS(status);
}
/* negative return value -> some internal error
* positive return value -> userns creation failed
* 0 -> userns creation succeeded
*/
static int create_user_ns(void)
{
pid_t pid;
pid = fork();
if (pid < 0)
return -1;
if (pid == 0) {
if (unshare(CLONE_NEWUSER))
_exit(EXIT_FAILURE);
_exit(EXIT_SUCCESS);
}
return wait_for_pid(pid);
}
Same difference since both codepaths hit the right spot in the kernel.
> +
> +static void test_userns_create_bpf(void)
> +{
> + __u32 cap_mask = 1ULL << CAP_SYS_ADMIN;
> + __u64 old_caps = 0;
> +
> + ASSERT_OK(create_new_user_ns(), "priv new user ns");
> +
> + cap_disable_effective(cap_mask, &old_caps);
> +
> + ASSERT_EQ(create_new_user_ns(), EPERM, "unpriv new user ns");
> +
> + if (cap_mask & old_caps)
> + cap_enable_effective(cap_mask, NULL);
> +}
> +
> +static void test_unpriv_userns_create_no_bpf(void)
> +{
> + __u32 cap_mask = 1ULL << CAP_SYS_ADMIN;
> + __u64 old_caps = 0;
> +
> + cap_disable_effective(cap_mask, &old_caps);
> +
> + ASSERT_OK(create_new_user_ns(), "no-bpf unpriv new user ns");
> +
> + if (cap_mask & old_caps)
> + cap_enable_effective(cap_mask, NULL);
> +}
> +
> +void test_deny_namespace(void)
> +{
> + struct test_deny_namespace *skel = NULL;
> + int err;
> +
> + if (test__start_subtest("unpriv_userns_create_no_bpf"))
> + test_unpriv_userns_create_no_bpf();
> +
> + skel = test_deny_namespace__open_and_load();
> + if (!ASSERT_OK_PTR(skel, "skel load"))
> + goto close_prog;
> +
> + err = test_deny_namespace__attach(skel);
> + if (!ASSERT_OK(err, "attach"))
> + goto close_prog;
> +
> + if (test__start_subtest("userns_create_bpf"))
> + test_userns_create_bpf();
> +
> + test_deny_namespace__detach(skel);
> +
> +close_prog:
> + test_deny_namespace__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_deny_namespace.c b/tools/testing/selftests/bpf/progs/test_deny_namespace.c
> new file mode 100644
> index 000000000000..9ec9dabc8372
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_deny_namespace.c
> @@ -0,0 +1,39 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +#include <errno.h>
> +#include <linux/capability.h>
> +
> +struct kernel_cap_struct {
> + __u32 cap[_LINUX_CAPABILITY_U32S_3];
> +} __attribute__((preserve_access_index));
> +
> +struct cred {
> + struct kernel_cap_struct cap_effective;
> +} __attribute__((preserve_access_index));
> +
> +char _license[] SEC("license") = "GPL";
> +
> +SEC("lsm/userns_create")
> +int BPF_PROG(test_userns_create, const struct cred *cred, int ret)
> +{
> + struct kernel_cap_struct caps = cred->cap_effective;
> + int cap_index = CAP_TO_INDEX(CAP_SYS_ADMIN);
> + __u32 cap_mask = CAP_TO_MASK(CAP_SYS_ADMIN);
> +
> + if (ret)
> + return 0;
> +
> + ret = -EPERM;
> + if (caps.cap[cap_index] & cap_mask)
> + return 0;
> +
> + return -EPERM;
> +}
Looks nice and simple.
Acked-by: Christian Brauner (Microsoft) <[email protected]>
On 7/22/22 1:07 AM, Martin KaFai Lau wrote:
> On Thu, Jul 21, 2022 at 12:28:07PM -0500, Frederick Lawler wrote:
>> The LSM hook userns_create was introduced to provide LSM's an
>> opportunity to block or allow unprivileged user namespace creation. This
>> test serves two purposes: it provides a test eBPF implementation, and
>> tests the hook successfully blocks or allows user namespace creation.
>>
>> This tests 4 cases:
>>
>> 1. Unattached bpf program does not block unpriv user namespace
>> creation.
>> 2. Attached bpf program allows user namespace creation given
>> CAP_SYS_ADMIN privileges.
>> 3. Attached bpf program denies user namespace creation for a
>> user without CAP_SYS_ADMIN.
>> 4. The sleepable implementation loads
>>
>> Signed-off-by: Frederick Lawler <[email protected]>
>>
>> ---
>> The generic deny_namespace file name is used for future namespace
>> expansion. I didn't want to limit these files to just the create_user_ns
>> hook.
>> Changes since v2:
>> - Rename create_user_ns hook to userns_create
>> Changes since v1:
>> - Introduce this patch
>> ---
>> .../selftests/bpf/prog_tests/deny_namespace.c | 88 +++++++++++++++++++
>> .../selftests/bpf/progs/test_deny_namespace.c | 39 ++++++++
>> 2 files changed, 127 insertions(+)
>> create mode 100644 tools/testing/selftests/bpf/prog_tests/deny_namespace.c
>> create mode 100644 tools/testing/selftests/bpf/progs/test_deny_namespace.c
>>
>> diff --git a/tools/testing/selftests/bpf/prog_tests/deny_namespace.c b/tools/testing/selftests/bpf/prog_tests/deny_namespace.c
>> new file mode 100644
>> index 000000000000..9e4714295008
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/prog_tests/deny_namespace.c
>> @@ -0,0 +1,88 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +#define _GNU_SOURCE
>> +#include <test_progs.h>
>> +#include "test_deny_namespace.skel.h"
>> +#include <sched.h>
>> +#include "cap_helpers.h"
>> +
>> +#define STACK_SIZE (1024 * 1024)
> Does the child need 1M stack space ?
No, I can reduce that.
>
>> +static char child_stack[STACK_SIZE];
>> +
>> +int clone_callback(void *arg)
> static
>
>> +{
>> + return 0;
>> +}
>> +
>> +static int create_new_user_ns(void)
>> +{
>> + int status;
>> + pid_t cpid;
>> +
>> + cpid = clone(clone_callback, child_stack + STACK_SIZE,
>> + CLONE_NEWUSER | SIGCHLD, NULL);
>> +
>> + if (cpid == -1)
>> + return errno;
>> +
>> + if (cpid == 0)
> Not an expert in clone() call and it is not clear what 0
> return value mean from the man page. Could you explain ?
>
Good catch. This is using the libc clone().
>> + return 0;
>> +
>> + waitpid(cpid, &status, 0);
>> + if (WIFEXITED(status))
>> + return WEXITSTATUS(status);
>> +
>> + return -1;
>> +}
>> +
>> +static void test_userns_create_bpf(void)
>> +{
>> + __u32 cap_mask = 1ULL << CAP_SYS_ADMIN;
>> + __u64 old_caps = 0;
>> +
>> + ASSERT_OK(create_new_user_ns(), "priv new user ns");
> Does it need to enable CAP_SYS_ADMIN first ?
>
You're right, this should be more explicitly set. I ran tests with the
vmtest.sh script supplied with sefltests/bpf which run under root. I
should always set CAP_SYS_ADMIN here to be consistent.
>> +
>> + cap_disable_effective(cap_mask, &old_caps);
>> +
>> + ASSERT_EQ(create_new_user_ns(), EPERM, "unpriv new user ns");
>> +
>> + if (cap_mask & old_caps)
>> + cap_enable_effective(cap_mask, NULL);
>> +}
>> +
>> +static void test_unpriv_userns_create_no_bpf(void)
>> +{
>> + __u32 cap_mask = 1ULL << CAP_SYS_ADMIN;
>> + __u64 old_caps = 0;
>> +
>> + cap_disable_effective(cap_mask, &old_caps);
>> +
>> + ASSERT_OK(create_new_user_ns(), "no-bpf unpriv new user ns");
>> +
>> + if (cap_mask & old_caps)
>> + cap_enable_effective(cap_mask, NULL);
>> +}
>> +
>> +void test_deny_namespace(void)
>> +{
>> + struct test_deny_namespace *skel = NULL;
>> + int err;
>> +
>> + if (test__start_subtest("unpriv_userns_create_no_bpf"))
>> + test_unpriv_userns_create_no_bpf();
>> +
>> + skel = test_deny_namespace__open_and_load();
>> + if (!ASSERT_OK_PTR(skel, "skel load"))
>> + goto close_prog;
>> +
>> + err = test_deny_namespace__attach(skel);
>> + if (!ASSERT_OK(err, "attach"))
>> + goto close_prog;
>> +
>> + if (test__start_subtest("userns_create_bpf"))
>> + test_userns_create_bpf();
>> +
>> + test_deny_namespace__detach(skel);
>> +
>> +close_prog:
>> + test_deny_namespace__destroy(skel);
>> +}
>> diff --git a/tools/testing/selftests/bpf/progs/test_deny_namespace.c b/tools/testing/selftests/bpf/progs/test_deny_namespace.c
>> new file mode 100644
>> index 000000000000..9ec9dabc8372
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/progs/test_deny_namespace.c
>> @@ -0,0 +1,39 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +#include <linux/bpf.h>
>> +#include <bpf/bpf_helpers.h>
>> +#include <bpf/bpf_tracing.h>
>> +#include <errno.h>
>> +#include <linux/capability.h>
>> +
>> +struct kernel_cap_struct {
>> + __u32 cap[_LINUX_CAPABILITY_U32S_3];
>> +} __attribute__((preserve_access_index));
>> +
>> +struct cred {
>> + struct kernel_cap_struct cap_effective;
>> +} __attribute__((preserve_access_index));
>> +
>> +char _license[] SEC("license") = "GPL";
>> +
>> +SEC("lsm/userns_create")
>> +int BPF_PROG(test_userns_create, const struct cred *cred, int ret)
>> +{
>> + struct kernel_cap_struct caps = cred->cap_effective;
>> + int cap_index = CAP_TO_INDEX(CAP_SYS_ADMIN);
>> + __u32 cap_mask = CAP_TO_MASK(CAP_SYS_ADMIN);
>> +
>> + if (ret)
>> + return 0;
>> +
>> + ret = -EPERM;
>> + if (caps.cap[cap_index] & cap_mask)
>> + return 0;
>> +
>> + return -EPERM;
>> +}
>> +
>> +SEC("lsm.s/userns_create")
>> +int BPF_PROG(test_sleepable_userns_create, const struct cred *cred, int ret)
>> +{
> An empty program is weird. If the intention is
> to ensure a sleepable program can attach to userns_create,
> move the test logic here and remove the non-sleepable
> program above.
>
Sure, I can do that.
>> + return 0;
>> +}
>> --
>> 2.30.2
>>