NAME¶

landlock_create_ruleset - create a new Landlock ruleset

LIBRARY¶

Standard C library (libc, -lc)

SYNOPSIS¶

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

int syscall(SYS_landlock_create_ruleset,
            const struct landlock_ruleset_attr *attr,
            size_t size , uint32_t flags);

DESCRIPTION¶

A Landlock ruleset identifies a set of rules (i.e., actions on objects). This landlock_create_ruleset() system call creates a new file descriptor which identifies a ruleset. This file descriptor can then be used by landlock_add_rule(2) and landlock_restrict_self(2). See landlock(7) for a global overview.

attr specifies the properties of the new ruleset. It points to the following structure:

struct landlock_ruleset_attr {


    __u64 handled_access_fs;


    __u64 handled_access_net;


    __u64 scoped;
};
    

handled_access_fs is a bitmask of handled filesystem actions (see Filesystem actions in landlock(7)).

handled_access_net is a bitmask of handled network actions (see Network actions in landlock(7)).

scoped is a bitmask of scope flags (see Scope flags in landlock(7)).

This structure defines a set of handled access rights, a set of actions on different object types, which should be denied by default when the ruleset is enacted. Vice versa, access rights that are not specifically listed here are not going to be denied by this ruleset when it is enacted.

For historical reasons, the LANDLOCK_ACCESS_FS_REFER right is always denied by default, even when its bit is not set in handled_access_fs. In order to add new rules with this access right, the bit must still be set explicitly (see Filesystem actions in landlock(7)).

The explicit listing of handled access rights is required for backwards compatibility reasons. In most use cases, processes that use Landlock will handle a wide range or all access rights that they know about at build time (and that they have tested with a kernel that supported them all).

This structure can grow in future Landlock versions.

size must be specified as sizeof(struct landlock_ruleset_attr) for compatibility reasons.

flags must be 0 if attr is used. Otherwise, flags can be set to:

LANDLOCK_CREATE_RULESET_VERSION

Return the highest supported Landlock ABI version (starting at 1). This version can be used for a best-effort security approach, which is encouraged when user space is not pinned to a specific kernel version.

Unless noted otherwise, all features documented in these manual pages are available with the version 1.

LANDLOCK_CREATE_RULESET_ERRATA

Return a bitmask of fixed issues for the current Landlock ABI version. If bit N is set (i.e., errata & (1 << (N - 1))), then erratum N has been fixed in the running kernel.

In addition to ABI versions, Landlock's errata mechanism tracks fixes for issues that may affect backwards compatibility or require userspace awareness.

Only check errata if your application specifically relies on behavior that changed due to the fix.

The full list of Landlock errata is available at https://docs.kernel.org/userspace-api/landlock.html#landlock-errata.

This flag is available on all Linux versions where Landlock errata were fixed. This specifically includes all newest bugfix releases of stable kernels where Landlock is supported.

If LANDLOCK_CREATE_RULESET_VERSION or LANDLOCK_CREATE_RULESET_ERRATA is set, then attr must be NULL and size must be 0.

RETURN VALUE¶

On success, landlock_create_ruleset() returns a new Landlock ruleset file descriptor, a Landlock ABI version, or a Landlock errata bitmask, according to flags.

On error, -1 is returned and errno is set to indicate the error.

ERRORS¶

landlock_create_ruleset() can fail for the following reasons:

E2BIG

size is too big.

EFAULT

attr was not a valid address.

EINVAL

Unknown flags, or unknown access, or unknown scope, or too small size.

EINVAL

Non-NULL attr or non-zero size in combination with LANDLOCK_CREATE_RULESET_VERSION or LANDLOCK_CREATE_RULESET_ERRATA.

ENOMSG

Empty accesses (i.e., attr did not specify any access rights to restrict).

EOPNOTSUPP

Landlock is supported by the kernel but disabled at boot time.

STANDARDS¶

Linux.

HISTORY¶

Linux 5.13.

EXAMPLES¶

See landlock(7).

SEE ALSO¶

landlock_add_rule(2), landlock_restrict_self(2), landlock(7)