Unverified Commit f4fba2d6 authored by Song Liu's avatar Song Liu Committed by Christian Brauner
Browse files

selftests/bpf: Add tests for bpf_cgroup_read_xattr 



Add tests for different scenarios with bpf_cgroup_read_xattr:
1. Read cgroup xattr from bpf_cgroup_from_id;
2. Read cgroup xattr from bpf_cgroup_ancestor;
3. Read cgroup xattr from css_iter;
4. Use bpf_cgroup_read_xattr in LSM hook security_socket_connect.
5. Use bpf_cgroup_read_xattr in cgroup program.

Signed-off-by: default avatarSong Liu <song@kernel.org>
Link: https://lore.kernel.org/20250623063854.1896364-5-song@kernel.org


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 1504d8c7

tools/testing/selftests/bpf/bpf_experimental.h

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Original line number Diff line number Diff line
@@ -596,4 +596,7 @@ extern int bpf_iter_dmabuf_new(struct bpf_iter_dmabuf *it) __weak __ksym; 
extern struct dma_buf *bpf_iter_dmabuf_next(struct bpf_iter_dmabuf *it) __weak __ksym;

extern void bpf_iter_dmabuf_destroy(struct bpf_iter_dmabuf *it) __weak __ksym;



extern int bpf_cgroup_read_xattr(struct cgroup *cgroup, const char *name__str,

				 struct bpf_dynptr *value_p) __weak __ksym;



#endif

tools/testing/selftests/bpf/prog_tests/cgroup_xattr.c

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// SPDX-License-Identifier: GPL-2.0-only

/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */



#include <errno.h>

#include <fcntl.h>

#include <sys/stat.h>

#include <string.h>

#include <unistd.h>

#include <sys/socket.h>

#include <sys/xattr.h>



#include <test_progs.h>



#include "read_cgroupfs_xattr.skel.h"

#include "cgroup_read_xattr.skel.h"



#define CGROUP_FS_ROOT "/sys/fs/cgroup/"

#define CGROUP_FS_PARENT CGROUP_FS_ROOT "foo/"

#define CGROUP_FS_CHILD CGROUP_FS_PARENT "bar/"



static int move_pid_to_cgroup(const char *cgroup_folder, pid_t pid)

{

	char filename[128];

	char pid_str[64];

	int procs_fd;

	int ret;



	snprintf(filename, sizeof(filename), "%scgroup.procs", cgroup_folder);

	snprintf(pid_str, sizeof(pid_str), "%d", pid);



	procs_fd = open(filename, O_WRONLY | O_APPEND);

	if (!ASSERT_OK_FD(procs_fd, "open"))

		return -1;



	ret = write(procs_fd, pid_str, strlen(pid_str));

	close(procs_fd);

	if (!ASSERT_GT(ret, 0, "write cgroup.procs"))

		return -1;

	return 0;

}



static void reset_cgroups_and_lo(void)

{

	rmdir(CGROUP_FS_CHILD);

	rmdir(CGROUP_FS_PARENT);

	system("ip addr del 1.1.1.1/32 dev lo");

	system("ip link set dev lo down");

}



static const char xattr_value_a[] = "bpf_selftest_value_a";

static const char xattr_value_b[] = "bpf_selftest_value_b";

static const char xattr_name[] = "user.bpf_test";



static int setup_cgroups_and_lo(void)

{

	int err;



	err = mkdir(CGROUP_FS_PARENT, 0755);

	if (!ASSERT_OK(err, "mkdir 1"))

		goto error;

	err = mkdir(CGROUP_FS_CHILD, 0755);

	if (!ASSERT_OK(err, "mkdir 2"))

		goto error;



	err = setxattr(CGROUP_FS_PARENT, xattr_name, xattr_value_a,

		       strlen(xattr_value_a) + 1, 0);

	if (!ASSERT_OK(err, "setxattr 1"))

		goto error;



	err = setxattr(CGROUP_FS_CHILD, xattr_name, xattr_value_b,

		       strlen(xattr_value_b) + 1, 0);

	if (!ASSERT_OK(err, "setxattr 2"))

		goto error;



	err = system("ip link set dev lo up");

	if (!ASSERT_OK(err, "lo up"))

		goto error;



	err = system("ip addr add 1.1.1.1 dev lo");

	if (!ASSERT_OK(err, "lo addr v4"))

		goto error;



	err = write_sysctl("/proc/sys/net/ipv4/ping_group_range", "0 0");

	if (!ASSERT_OK(err, "write_sysctl"))

		goto error;



	return 0;

error:

	reset_cgroups_and_lo();

	return err;

}



static void test_read_cgroup_xattr(void)

{

	struct sockaddr_in sa4 = {

		.sin_family = AF_INET,

		.sin_addr.s_addr = htonl(INADDR_LOOPBACK),

	};

	struct read_cgroupfs_xattr *skel = NULL;

	pid_t pid = gettid();

	int sock_fd = -1;

	int connect_fd = -1;



	if (!ASSERT_OK(setup_cgroups_and_lo(), "setup_cgroups_and_lo"))

		return;

	if (!ASSERT_OK(move_pid_to_cgroup(CGROUP_FS_CHILD, pid),

		       "move_pid_to_cgroup"))

		goto out;



	skel = read_cgroupfs_xattr__open_and_load();

	if (!ASSERT_OK_PTR(skel, "read_cgroupfs_xattr__open_and_load"))

		goto out;



	skel->bss->target_pid = pid;



	if (!ASSERT_OK(read_cgroupfs_xattr__attach(skel), "read_cgroupfs_xattr__attach"))

		goto out;



	sock_fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_ICMP);

	if (!ASSERT_OK_FD(sock_fd, "sock create"))

		goto out;



	connect_fd = connect(sock_fd, &sa4, sizeof(sa4));

	if (!ASSERT_OK_FD(connect_fd, "connect 1"))

		goto out;

	close(connect_fd);



	ASSERT_TRUE(skel->bss->found_value_a, "found_value_a");

	ASSERT_TRUE(skel->bss->found_value_b, "found_value_b");



out:

	close(connect_fd);

	close(sock_fd);

	read_cgroupfs_xattr__destroy(skel);

	move_pid_to_cgroup(CGROUP_FS_ROOT, pid);

	reset_cgroups_and_lo();

}



void test_cgroup_xattr(void)

{

	RUN_TESTS(cgroup_read_xattr);



	if (test__start_subtest("read_cgroupfs_xattr"))

		test_read_cgroup_xattr();

}

tools/testing/selftests/bpf/progs/cgroup_read_xattr.c

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+158 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */



#include <vmlinux.h>

#include <bpf/bpf_tracing.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_core_read.h>

#include "bpf_experimental.h"

#include "bpf_misc.h"



char _license[] SEC("license") = "GPL";



char value[16];



static __always_inline void read_xattr(struct cgroup *cgroup)

{

	struct bpf_dynptr value_ptr;



	bpf_dynptr_from_mem(value, sizeof(value), 0, &value_ptr);

	bpf_cgroup_read_xattr(cgroup, "user.bpf_test",

			      &value_ptr);

}



SEC("lsm.s/socket_connect")

__success

int BPF_PROG(trusted_cgroup_ptr_sleepable)

{

	u64 cgrp_id = bpf_get_current_cgroup_id();

	struct cgroup *cgrp;



	cgrp = bpf_cgroup_from_id(cgrp_id);

	if (!cgrp)

		return 0;



	read_xattr(cgrp);

	bpf_cgroup_release(cgrp);

	return 0;

}



SEC("lsm/socket_connect")

__success

int BPF_PROG(trusted_cgroup_ptr_non_sleepable)

{

	u64 cgrp_id = bpf_get_current_cgroup_id();

	struct cgroup *cgrp;



	cgrp = bpf_cgroup_from_id(cgrp_id);

	if (!cgrp)

		return 0;



	read_xattr(cgrp);

	bpf_cgroup_release(cgrp);

	return 0;

}



SEC("lsm/socket_connect")

__success

int BPF_PROG(use_css_iter_non_sleepable)

{

	u64 cgrp_id = bpf_get_current_cgroup_id();

	struct cgroup_subsys_state *css;

	struct cgroup *cgrp;



	cgrp = bpf_cgroup_from_id(cgrp_id);

	if (!cgrp)

		return 0;



	bpf_for_each(css, css, &cgrp->self, BPF_CGROUP_ITER_ANCESTORS_UP)

		read_xattr(css->cgroup);



	bpf_cgroup_release(cgrp);

	return 0;

}



SEC("lsm.s/socket_connect")

__failure __msg("expected an RCU CS")

int BPF_PROG(use_css_iter_sleepable_missing_rcu_lock)

{

	u64 cgrp_id = bpf_get_current_cgroup_id();

	struct cgroup_subsys_state *css;

	struct cgroup *cgrp;



	cgrp = bpf_cgroup_from_id(cgrp_id);

	if (!cgrp)

		return 0;



	bpf_for_each(css, css, &cgrp->self, BPF_CGROUP_ITER_ANCESTORS_UP)

		read_xattr(css->cgroup);



	bpf_cgroup_release(cgrp);

	return 0;

}



SEC("lsm.s/socket_connect")

__success

int BPF_PROG(use_css_iter_sleepable_with_rcu_lock)

{

	u64 cgrp_id = bpf_get_current_cgroup_id();

	struct cgroup_subsys_state *css;

	struct cgroup *cgrp;



	bpf_rcu_read_lock();

	cgrp = bpf_cgroup_from_id(cgrp_id);

	if (!cgrp)

		goto out;



	bpf_for_each(css, css, &cgrp->self, BPF_CGROUP_ITER_ANCESTORS_UP)

		read_xattr(css->cgroup);



	bpf_cgroup_release(cgrp);

out:

	bpf_rcu_read_unlock();

	return 0;

}



SEC("lsm/socket_connect")

__success

int BPF_PROG(use_bpf_cgroup_ancestor)

{

	u64 cgrp_id = bpf_get_current_cgroup_id();

	struct cgroup *cgrp, *ancestor;



	cgrp = bpf_cgroup_from_id(cgrp_id);

	if (!cgrp)

		return 0;



	ancestor = bpf_cgroup_ancestor(cgrp, 1);

	if (!ancestor)

		goto out;



	read_xattr(cgrp);

	bpf_cgroup_release(ancestor);

out:

	bpf_cgroup_release(cgrp);

	return 0;

}



SEC("cgroup/sendmsg4")

__success

int BPF_PROG(cgroup_skb)

{

	u64 cgrp_id = bpf_get_current_cgroup_id();

	struct cgroup *cgrp, *ancestor;



	cgrp = bpf_cgroup_from_id(cgrp_id);

	if (!cgrp)

		return 0;



	ancestor = bpf_cgroup_ancestor(cgrp, 1);

	if (!ancestor)

		goto out;



	read_xattr(cgrp);

	bpf_cgroup_release(ancestor);

out:

	bpf_cgroup_release(cgrp);

	return 0;

}

tools/testing/selftests/bpf/progs/read_cgroupfs_xattr.c

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+60 −0
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// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */



#include <vmlinux.h>

#include <bpf/bpf_tracing.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_core_read.h>

#include "bpf_experimental.h"



char _license[] SEC("license") = "GPL";



pid_t target_pid = 0;



char xattr_value[64];

static const char expected_value_a[] = "bpf_selftest_value_a";

static const char expected_value_b[] = "bpf_selftest_value_b";

bool found_value_a;

bool found_value_b;



SEC("lsm.s/socket_connect")

int BPF_PROG(test_socket_connect)

{

	u64 cgrp_id = bpf_get_current_cgroup_id();

	struct cgroup_subsys_state *css, *tmp;

	struct bpf_dynptr value_ptr;

	struct cgroup *cgrp;



	if ((bpf_get_current_pid_tgid() >> 32) != target_pid)

		return 0;



	bpf_rcu_read_lock();

	cgrp = bpf_cgroup_from_id(cgrp_id);

	if (!cgrp) {

		bpf_rcu_read_unlock();

		return 0;

	}



	css = &cgrp->self;

	bpf_dynptr_from_mem(xattr_value, sizeof(xattr_value), 0, &value_ptr);

	bpf_for_each(css, tmp, css, BPF_CGROUP_ITER_ANCESTORS_UP) {

		int ret;



		ret = bpf_cgroup_read_xattr(tmp->cgroup, "user.bpf_test",

					    &value_ptr);

		if (ret < 0)

			continue;



		if (ret == sizeof(expected_value_a) &&

		    !bpf_strncmp(xattr_value, sizeof(expected_value_a), expected_value_a))

			found_value_a = true;

		if (ret == sizeof(expected_value_b) &&

		    !bpf_strncmp(xattr_value, sizeof(expected_value_b), expected_value_b))

			found_value_b = true;

	}



	bpf_rcu_read_unlock();

	bpf_cgroup_release(cgrp);



	return 0;

}