selftests/bpf: add new negative tests for xattr related BPF kfuncs

Add a set of negative tests to verify the newly enforced constraints
applied to xattr related BPF kfuncs.

Signed-off-by: Matt Bobrowski <mattbobrowski@google.com>

Author: mattbobrowski

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

@@ -115,18 +115,18 @@ static void validate_bar_removed(struct test_set_remove_xattr *skel)
 static void test_set_remove_xattr(void)
 {
 	struct test_set_remove_xattr *skel = NULL;
-	int fd = -1, err;
+	int fd, err;
 
 	fd = open(testfile, O_CREAT | O_RDONLY, 0644);
 	if (!ASSERT_GE(fd, 0, "create_file"))
 		return;
 
 	close(fd);
-	fd = -1;
 
 	skel = test_set_remove_xattr__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "test_set_remove_xattr__open_and_load"))
-		return;
+		goto out;
+
 
 	/* Set security.bpf.foo to "hello" */
 	err = setxattr(testfile, skel->rodata->xattr_foo, value_foo, strlen(value_foo) + 1, 0);
@@ -188,8 +188,16 @@ static void test_set_remove_xattr(void)
 	ASSERT_TRUE(skel->bss->locked_remove_security_selinux_fail,
 		    "locked_remove_security_selinux_fail");
 
+	ASSERT_EQ(skel->bss->ret_code_name_empty, -ERANGE,
+		  "ret_code_name_empty");
+	ASSERT_EQ(skel->bss->ret_code_name_too_long, -ERANGE,
+		  "ret_code_name_too_long");
+	ASSERT_EQ(skel->bss->ret_code_value_too_large, -E2BIG,
+		  "ret_code_value_too_large");
+	ASSERT_EQ(skel->bss->ret_code_invalid_flags, -EINVAL,
+		  "ret_code_invalid_flags");
+
 out:
-	close(fd);
 	test_set_remove_xattr__destroy(skel);
 	remove(testfile);
 }

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

@@ -17,6 +17,14 @@ static const char xattr_selinux[] = "security.selinux";
 char value_bar[] = "world";
 char read_value[32];
 
+const char xattr_negative[] = "security.bpf.negative";
+int ret_code_name_empty;
+int ret_code_name_too_long;
+int ret_code_value_too_large;
+int ret_code_invalid_flags;
+const char long_name[] = "security.bpf.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+char large_value[65537];
+
 bool set_security_bpf_bar_success;
 bool remove_security_bpf_bar_success;
 bool set_security_selinux_fail;
@@ -73,6 +81,19 @@ int BPF_PROG(test_inode_getxattr, struct dentry *dentry, char *name)
 			remove_security_selinux_fail = true;
 	}
 
+	bpf_dynptr_from_mem(read_value, sizeof(read_value), 0, &value_ptr);
+	ret_code_name_empty = bpf_get_dentry_xattr(dentry, "", &value_ptr);
+	ret_code_name_too_long =
+		bpf_get_dentry_xattr(dentry, long_name, &value_ptr);
+
+	bpf_dynptr_from_mem(large_value, sizeof(large_value), 0, &value_ptr);
+	ret_code_value_too_large =
+		bpf_set_dentry_xattr(dentry, xattr_negative, &value_ptr, 0);
+
+	bpf_dynptr_from_mem(value_bar, sizeof(value_bar), 0, &value_ptr);
+	ret_code_invalid_flags = bpf_set_dentry_xattr(dentry, xattr_negative,
+						      &value_ptr, 0xFFFF);
+
 	return 0;
 }