Commit 8681156c authored by Song Liu's avatar Song Liu Committed by Alexei Starovoitov
Browse files

selftests/bpf: Add tests for bpf_get_dentry_xattr 



Add test for bpf_get_dentry_xattr on hook security_inode_getxattr.
Verify that the kfunc can read the xattr. Also test failing getxattr
from user space by returning non-zero from the LSM bpf program.

Acked-by: default avatarChristian Brauner <brauner@kernel.org>
Signed-off-by: default avatarSong Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240806230904.71194-4-song@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent ac13a426

tools/testing/selftests/bpf/bpf_kfuncs.h

+10 −1
Original line number Diff line number Diff line
@@ -45,7 +45,7 @@ extern int bpf_dynptr_clone(const struct bpf_dynptr *ptr, struct bpf_dynptr *clo 


/* Description

 *  Modify the address of a AF_UNIX sockaddr.

 * Returns__bpf_kfunc

 * Returns

 *  -EINVAL if the address size is too big or, 0 if the sockaddr was successfully modified.

 */

extern int bpf_sock_addr_set_sun_path(struct bpf_sock_addr_kern *sa_kern,
@@ -78,4 +78,13 @@ extern int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_ptr, 


extern bool bpf_session_is_return(void) __ksym __weak;

extern __u64 *bpf_session_cookie(void) __ksym __weak;



struct dentry;

/* Description

 *  Returns xattr of a dentry

 * Returns

 *  Error code

 */

extern int bpf_get_dentry_xattr(struct dentry *dentry, const char *name,

			      struct bpf_dynptr *value_ptr) __ksym __weak;

#endif

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

+8 −1
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ static void test_xattr(void) 
{

	struct test_get_xattr *skel = NULL;

	int fd = -1, err;

	int v[32];



	fd = open(testfile, O_CREAT | O_RDONLY, 0644);

	if (!ASSERT_GE(fd, 0, "create_file"))
@@ -50,7 +51,13 @@ static void test_xattr(void) 
	if (!ASSERT_GE(fd, 0, "open_file"))

		goto out;



	ASSERT_EQ(skel->bss->found_xattr, 1, "found_xattr");

	ASSERT_EQ(skel->bss->found_xattr_from_file, 1, "found_xattr_from_file");



	/* Trigger security_inode_getxattr */

	err = getxattr(testfile, "user.kfuncs", v, sizeof(v));

	ASSERT_EQ(err, -1, "getxattr_return");

	ASSERT_EQ(errno, EINVAL, "getxattr_errno");

	ASSERT_EQ(skel->bss->found_xattr_from_dentry, 1, "found_xattr_from_dentry");



out:

	close(fd);

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

+32 −5
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */



#include "vmlinux.h"

#include <errno.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>

#include "bpf_kfuncs.h"
@@ -9,10 +10,12 @@ 
char _license[] SEC("license") = "GPL";



__u32 monitored_pid;

__u32 found_xattr;

__u32 found_xattr_from_file;

__u32 found_xattr_from_dentry;



static const char expected_value[] = "hello";

char value[32];

char value1[32];

char value2[32];



SEC("lsm.s/file_open")

int BPF_PROG(test_file_open, struct file *f)
@@ -25,13 +28,37 @@ int BPF_PROG(test_file_open, struct file *f) 
	if (pid != monitored_pid)

		return 0;



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

	bpf_dynptr_from_mem(value1, sizeof(value1), 0, &value_ptr);



	ret = bpf_get_file_xattr(f, "user.kfuncs", &value_ptr);

	if (ret != sizeof(expected_value))

		return 0;

	if (bpf_strncmp(value, ret, expected_value))

	if (bpf_strncmp(value1, ret, expected_value))

		return 0;

	found_xattr = 1;

	found_xattr_from_file = 1;

	return 0;

}



SEC("lsm.s/inode_getxattr")

int BPF_PROG(test_inode_getxattr, struct dentry *dentry, char *name)

{

	struct bpf_dynptr value_ptr;

	__u32 pid;

	int ret;



	pid = bpf_get_current_pid_tgid() >> 32;

	if (pid != monitored_pid)

		return 0;



	bpf_dynptr_from_mem(value2, sizeof(value2), 0, &value_ptr);



	ret = bpf_get_dentry_xattr(dentry, "user.kfuncs", &value_ptr);

	if (ret != sizeof(expected_value))

		return 0;

	if (bpf_strncmp(value2, ret, expected_value))

		return 0;

	found_xattr_from_dentry = 1;



	/* return non-zero to fail getxattr from user space */

	return -EINVAL;

}