[PATCH v1 2/4] landlock_create_ruleset.2: Document new syscall

[Mickaël Salaün]

From: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx>

This is an adaptation of
https://www.kernel.org/doc/html/v5.13/userspace-api/landlock.html

Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210706182217.32338-3-mic@xxxxxxxxxxx
---
 man2/landlock_create_ruleset.2 | 134 +++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 man2/landlock_create_ruleset.2

diff --git a/man2/landlock_create_ruleset.2 b/man2/landlock_create_ruleset.2
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+.\" Copyright © 2017-2020 Mickaël Salaün <mic@xxxxxxxxxxx>
+.\" Copyright © 2019-2020 ANSSI
+.\" Copyright © 2021 Microsoft Corporation
+.\"
+.\" %%%LICENSE_START(VERBATIM)
+.\" Permission is granted to make and distribute verbatim copies of this
+.\" manual provided the copyright notice and this permission notice are
+.\" preserved on all copies.
+.\"
+.\" Permission is granted to copy and distribute modified versions of this
+.\" manual under the conditions for verbatim copying, provided that the
+.\" entire resulting derived work is distributed under the terms of a
+.\" permission notice identical to this one.
+.\"
+.\" Since the Linux kernel and libraries are constantly changing, this
+.\" manual page may be incorrect or out-of-date.  The author(s) assume no
+.\" responsibility for errors or omissions, or for damages resulting from
+.\" the use of the information contained herein.  The author(s) may not
+.\" have taken the same level of care in the production of this manual,
+.\" which is licensed free of charge, as they might when working
+.\" professionally.
+.\"
+.\" Formatted or processed versions of this manual, if unaccompanied by
+.\" the source, must acknowledge the copyright and authors of this work.
+.\" %%%LICENSE_END
+.\"
+.TH LANDLOCK_CREATE_RULESET 2 2021-06-27 Linux "Linux Programmer's Manual"
+.SH NAME
+landlock_create_ruleset \- create a new Landlock ruleset
+.SH SYNOPSIS
+.nf
+.BR "#include <linux/landlock.h>" "  /* Definition of " LANDLOCK_* " constants */"
+.BR "#include <sys/syscall.h>" "     /* Definition of " SYS_* " constants */"
+.PP
+.BI "int syscall(SYS_landlock_create_ruleset,
+.BI "            const struct landlock_ruleset_attr " attr ,
+.BI "            size_t " size " , __u32 " flags );
+.SH DESCRIPTION
+A Landlock ruleset identifies a set of rules (i.e. actions on objects).
+This
+.BR landlock_create_ruleset (2)
+system call enables creating a new file descriptor identifying a ruleset.
+This file descriptor can then be used by
+.BR landlock_add_rule (2)
+and
+.BR landlock_restrict_self (2)
+\&.  See
+.BR landlock (7)
+for a global overview.
+.PP
+.I attr
+specifies the properties of the new ruleset.  It points to the following
+structure:
+.IP
+.in +4n
+.EX
+struct landlock_ruleset_attr {
+	__u64 handled_access_fs;
+};
+.EE
+.in
+.IP
+.I handled_access_fs
+is a bitmask of actions that is handled by this ruleset and should then be
+forbidden if no rule explicitly allow them
+(see
+.BR "Filesystem actions"
+in
+.BR landlock (7)
+).
+This enables simply restricting ambient rights (e.g., global filesystem
+access) and is needed for compatibility reasons.
+.PP
+.I size
+must be specified as
+.I sizeof(struct landlock_ruleset_attr)
+for compatibility reasons.
+.PP
+.I flags
+must be 0 if
+.I attr
+is used.  Otherwise,
+.I flags
+can be set to:
+.TP
+.BR LANDLOCK_CREATE_RULESET_VERSION
+If
+.I attr
+is NULL and
+.I size
+is 0, then the returned value is 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.  All features documented in these man pages are available
+with the version 1.
+.SH RETURN VALUE
+On success,
+.BR landlock_create_ruleset (2)
+returns a new Landlock ruleset file descriptor, or a Landlock ABI version
+according to
+.I flags
+\&.
+.SH ERRORS
+.BR landlock_create_ruleset (2)
+can failed for the following reasons:
+.TP
+.BR EOPNOTSUPP
+Landlock is supported by the kernel but disabled at boot time.
+.TP
+.BR EINVAL
+Unknown
+.I flags
+, or unknown access, or too small
+.I size
+\&.
+.TP
+.BR E2BIG
+.I size
+is too big.
+.TP
+.BR EFAULT
+.I attr
+was not a valid address.
+.TP
+.BR ENOMSG
+Empty accesses (i.e.
+.I attr->handled_access_fs
+is 0).
+.SH VERSIONS
+Landlock was added in Linux 5.13.
+.SH SEE ALSO
+.BR landlock (7),
+.BR landlock_add_rule (2),
+.BR landlock_restrict_self (2)
-- 
2.32.0