NAME

landlock_add_rule - add a new Landlock rule to a ruleset

LIBRARY

Standard C library (libc, -lc)

SYNOPSIS

#include <linux/landlock.h>  /* Definition of LANDLOCK_* constants */
#include <sys/syscall.h>     /* Definition of SYS_* constants */

int syscall(SYS_landlock_add_rule, int ruleset_fd,
            enum landlock_rule_type rule_type,
            const void *rule_attr, uint32_t flags);

DESCRIPTION

A Landlock rule describes an action on an object. An object is currently a file hierarchy, and the related filesystem actions are defined with a set of access rights. This landlock_add_rule() system call enables adding a new Landlock rule to an existing ruleset created with landlock_create_ruleset(2). See landlock(7) for a global overview.

ruleset_fd is a Landlock ruleset file descriptor obtained with landlock_create_ruleset(2).

rule_type identifies the structure type pointed to by rule_attr. Currently, Linux supports the following rule_type value:

LANDLOCK_RULE_PATH_BENEATH: This defines the object type as a file hierarchy. In this case, rule_attr points to the following structure:

struct landlock_path_beneath_attr {
    __u64 allowed_access;
    __s32 parent_fd;
} __attribute__((packed));

allowed_access contains a bitmask of allowed filesystem actions for this file hierarchy (see Filesystem actions in landlock(7)).

parent_fd is an opened file descriptor, preferably with the O_PATH flag, which identifies the parent directory of the file hierarchy or just a file.

flags must be 0.

RETURN VALUE

On success, landlock_add_rule() returns 0.

ERRORS

landlock_add_rule() can fail for the following reasons:

EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time.
EINVAL: flags is not 0, or the rule accesses are inconsistent (i.e., rule_attr->allowed_access is not a subset of the ruleset handled accesses).
ENOMSG: Empty accesses (i.e., rule_attr->allowed_access is 0).
EBADF: ruleset_fd is not a file descriptor for the current thread, or a member of rule_attr is not a file descriptor as expected.
EBADFD: ruleset_fd is not a ruleset file descriptor, or a member of rule_attr is not the expected file descriptor type.
EPERM: ruleset_fd has no write access to the underlying ruleset.
EFAULT: rule_attr was not a valid address.

STANDARDS

Linux.

HISTORY

Linux 5.13.

EXAMPLES

See landlock(7).