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: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Song Liu <song@xxxxxxxxxx>
---
tools/testing/selftests/bpf/bpf_kfuncs.h | 8 ++++
.../selftests/bpf/prog_tests/fs_kfuncs.c | 9 ++++-
.../selftests/bpf/progs/test_get_xattr.c | 37 ++++++++++++++++---
3 files changed, 48 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h b/tools/testing/selftests/bpf/bpf_kfuncs.h
index 3b6675ab4086..cf25421c36c9 100644
--- a/tools/testing/selftests/bpf/bpf_kfuncs.h
+++ b/tools/testing/selftests/bpf/bpf_kfuncs.h
@@ -78,4 +78,12 @@ 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;
+
+/* Description
+ * Returns xattr of a dentry
+ * Returns__bpf_kfunc
+ * Error code
+ */
+extern int bpf_get_dentry_xattr(struct dentry *dentry, const char *name,
+ struct bpf_dynptr *value_ptr) __ksym __weak;
#endif
diff --git a/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c b/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
index 37056ba73847..5a0b51157451 100644
--- a/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
+++ b/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
@@ -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);
diff --git a/tools/testing/selftests/bpf/progs/test_get_xattr.c b/tools/testing/selftests/bpf/progs/test_get_xattr.c
index 7eb2a4e5a3e5..66e737720f7c 100644
--- a/tools/testing/selftests/bpf/progs/test_get_xattr.c
+++ b/tools/testing/selftests/bpf/progs/test_get_xattr.c
@@ -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;
+}
--
2.43.5
