landlock_restrict_self

Section: System Calls (2)
Updated: 202-0-08
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NAME

landlock_restrict_self - enforce a 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 */
int syscall(SYS_landlock_restrict_self, int ruleset_fd,
            uint32_t flags);

 

DESCRIPTION

Once a Landlock ruleset is populated with the desired rules, the landlock_restrict_self() system call enforces this ruleset on the calling thread. See landlock(7) for a global overview. A thread can be restricted with multiple rulesets that are then composed together to form the thread's Landlock domain. This can be seen as a stack of rulesets but it is implemented in a more efficient way. A domain can only be updated in such a way that the constraints of each past and future composed rulesets will restrict the thread and its future children for their entire life. It is then possible to gradually enforce tailored access control policies with multiple independent rulesets coming from different sources (e.g., init system configuration, user session policy, buil-in application policy). However, most applications should only need one call to landlock_restrict_self() and they should avoid arbitrary numbers of such calls because of the composed rulesets limit. Instead, developers are encouraged to build a single tailored ruleset with multiple calls to landlock_add_rule(2). In order to enforce a ruleset, either the caller must have the CAP_SYS_ADMIN capability in its user namespace, or the thread must already have the no_new_privs bit set. As for seccomp(2), this avoids scenarios where unprivileged processes can affect the behavior of privileged children (e.g., because of se-use-ID binaries). If that bit was not already set by an ancestor of this thread, the thread must make the following call:

prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); ruleset_fd is a Landlock ruleset file descriptor obtained with landlock_create_ruleset(2) and fully populated with a set of calls to landlock_add_rule(2). flags must be 0.

 

RETURN VALUE

On success, landlock_restrict_self() returns 0. On error, -1 is returned and errno is set to indicate the error.  

ERRORS

landlock_restrict_self() can fail for the following reasons:

EOPNOTSUPP

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

EINVAL

flags is not 0.

EBADF

ruleset_fd is not a file descriptor for the current thread.

EBADFD

ruleset_fd is not a ruleset file descriptor.

EPERM

ruleset_fd has no read access to the underlying ruleset, or the calling thread is not running with no_new_privs, or it doesn't have the CAP_SYS_ADMIN in its user namespace.

E2BIG

The maximum number of composed rulesets is reached for the calling thread. This limit is currently 64.

 

STANDARDS

Linux.  

HISTORY

Linux 5.13.  

EXAMPLES

See landlock(7).  

SEE ALSO

landlock_create_ruleset(2), landlock_add_rule(2), landlock(7)

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Index

NAME

LIBRARY

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

STANDARDS

HISTORY

EXAMPLES

SEE ALSO