[PATCH v3 0/4] Update Landlock docs to Landlock ABI v8

[PATCH v3 0/4] Update Landlock docs to Landlock ABI v8

[Günther Noack]

Hello!

Thanks for the review, Alejandro!  Here's the third round of the patch
set to bring the Landlock manpages up to speed with Landlock ABI v8.

Change Log
==========

v3:
  - split the size/attr clarifications from the "errata" patch into a
    separate commit
  - earlier patch from v2 about the "scoped" EINVAL error was already
    merged
  
v2:
  - landlock_create_ruleset.2: added a tiny patch to add a missing
    mention of "scoped" in the errors list.
  - landlock_create_ruleset.2: various reformulations for errata
  - earlier patch from v1 about the default ABI version assumption was
    already merged (thanks!)    

Günther Noack (4):
  man/man2/landlock_create_ruleset.2: Clarify attr and size constraints
  man/man[27]/{landlock_create_ruleset.2,landlock.7}: Document
    LANDLOCK_CREATE_RULESET_ERRATA
  man/man[27]/{landlock_restrict_self.2,landlock.7}: Document
    LANDLOCK_RESTRICT_SELF_TSYNC (ABI v8)
  man/man2/landlock_restrict_self.2: Document ABI requirement for
    logging flags

 man/man2/landlock_create_ruleset.2 | 57 ++++++++++++++++++++++++++----
 man/man2/landlock_restrict_self.2  | 20 +++++++++++
 man/man7/landlock.7                |  2 ++
 3 files changed, 73 insertions(+), 6 deletions(-)

-- 
2.53.0

[PATCH v3 1/4] man/man2/landlock_create_ruleset.2: Clarify attr and size constraints

[Günther Noack]

When used with special flags like LANDLOCK_CREATE_RULESET_VERSION,
attr must be NULL and size must be 0.

Signed-off-by: Günther Noack <gnoack3000@gmail.com>
---
 man/man2/landlock_create_ruleset.2 | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/man/man2/landlock_create_ruleset.2 b/man/man2/landlock_create_ruleset.2
index d4eb5d827656..dd14f0ceba7c 100644
--- a/man/man2/landlock_create_ruleset.2
+++ b/man/man2/landlock_create_ruleset.2
@@ -116,11 +116,7 @@ Otherwise,
 can be set to:
 .TP
 .B 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
+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
@@ -129,6 +125,15 @@ version.
 Unless noted otherwise,
 all features documented in these manual pages are available with the
 version 1.
+.P
+If
+.B LANDLOCK_CREATE_RULESET_VERSION
+is set,
+then
+.I attr
+must be NULL and
+.I size
+must be 0.
 .SH RETURN VALUE
 On success,
 .BR landlock_create_ruleset ()
@@ -159,6 +164,14 @@ Unknown
 or unknown access, or unknown scope, or too small
 .IR size .
 .TP
+.B EINVAL
+Non-NULL
+.I attr
+or non-zero
+.I size
+in combination with
+.BR LANDLOCK_CREATE_RULESET_VERSION .
+.TP
 .B ENOMSG
 Empty accesses (i.e.,
 .I attr
-- 
2.53.0

[PATCH v3 2/4] man/man[27]/{landlock_create_ruleset.2,landlock.7}: Document LANDLOCK_CREATE_RULESET_ERRATA

[Günther Noack]

Document the LANDLOCK_CREATE_RULESET_ERRATA flag, which returns a
bitmask of fixed issues for the current Landlock ABI version.

This mechanism was introduced in Linux 6.15, but backported to all
older kernel releases where these errata fixes were backported to.
On official Linux kernel releases, if landlock_create_ruleset() with
LANDLOCK_CREATE_RULESET_ERRATA returns an error, this is equivalent to
the case where none of the known errata have been fixed.

Signed-off-by: Günther Noack <gnoack3000@gmail.com>
---
 man/man2/landlock_create_ruleset.2 | 36 ++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/man/man2/landlock_create_ruleset.2 b/man/man2/landlock_create_ruleset.2
index dd14f0ceba7c..9520c7269742 100644
--- a/man/man2/landlock_create_ruleset.2
+++ b/man/man2/landlock_create_ruleset.2
@@ -125,9 +125,38 @@ version.
 Unless noted otherwise,
 all features documented in these manual pages are available with the
 version 1.
+.TP
+.B LANDLOCK_CREATE_RULESET_ERRATA
+Return a bitmask of fixed issues
+for the current Landlock ABI version.
+If bit N is set (i.e.,
+.IR "errata & (1 << (N - 1))" ),
+then erratum N has been fixed in the running kernel.
+.IP
+In addition to ABI versions,
+Landlock's errata mechanism
+tracks fixes for issues that
+may affect backwards compatibility
+or require userspace awareness.
+.IP
+Only check errata if your application specifically relies on behavior
+that changed due to the fix.
+.IP
+The full list of Landlock errata is available at
+.UR https:\://docs.kernel.org/userspace\-api/landlock.html#landlock\-errata
+.UE .
+.IP
+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.
 .P
 If
 .B LANDLOCK_CREATE_RULESET_VERSION
+or
+.B LANDLOCK_CREATE_RULESET_ERRATA
 is set,
 then
 .I attr
@@ -138,7 +167,8 @@ must be 0.
 On success,
 .BR landlock_create_ruleset ()
 returns a new Landlock ruleset file descriptor,
-or a Landlock ABI version,
+a Landlock ABI version,
+or a Landlock errata bitmask,
 according to
 .IR flags .
 .P
@@ -170,7 +200,9 @@ Non-NULL
 or non-zero
 .I size
 in combination with
-.BR LANDLOCK_CREATE_RULESET_VERSION .
+.B LANDLOCK_CREATE_RULESET_VERSION
+or
+.BR LANDLOCK_CREATE_RULESET_ERRATA .
 .TP
 .B ENOMSG
 Empty accesses (i.e.,
-- 
2.53.0

[PATCH v3 3/4] man/man[27]/{landlock_restrict_self.2,landlock.7}: Document LANDLOCK_RESTRICT_SELF_TSYNC (ABI v8)

[Günther Noack]

Document the new LANDLOCK_RESTRICT_SELF_TSYNC flag, which applies the
Landlock configuration atomically to all threads of the calling process.

Available since Linux 7.0 (Landlock ABI version 8).

Signed-off-by: Günther Noack <gnoack3000@gmail.com>
---
 man/man2/landlock_restrict_self.2 | 18 ++++++++++++++++++
 man/man7/landlock.7               |  2 ++
 2 files changed, 20 insertions(+)

diff --git a/man/man2/landlock_restrict_self.2 b/man/man2/landlock_restrict_self.2
index 9e80a40ee4a4..1265ea2feb91 100644
--- a/man/man2/landlock_restrict_self.2
+++ b/man/man2/landlock_restrict_self.2
@@ -133,6 +133,24 @@ It can also be used with a
 .I ruleset_fd
 value of \-1 to mute subdomain logs
 without creating a domain.
+.P
+The following flag supports policy enforcement in multithreaded processes:
+.TP
+.B LANDLOCK_RESTRICT_SELF_TSYNC
+Applies the new Landlock configuration atomically
+to all threads of the current process,
+including the Landlock domain and logging configuration.
+This overrides the Landlock configuration of sibling threads,
+irrespective of previously established Landlock domains
+and logging configurations on those threads.
+.IP
+If the calling thread is running with
+.IR no_new_privs ,
+this operation enables
+.I no_new_privs
+on the sibling threads as well.
+.IP
+This flag is available since Landlock ABI version 8.
 .SH RETURN VALUE
 On success,
 .BR landlock_restrict_self ()
diff --git a/man/man7/landlock.7 b/man/man7/landlock.7
index bcf06ea30ad4..06910ccab5b1 100644
--- a/man/man7/landlock.7
+++ b/man/man7/landlock.7
@@ -476,6 +476,8 @@ _	_	_
 7	6.15	LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF
 \^	\^	LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON
 \^	\^	LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF
+_	_	_
+8	7.0	LANDLOCK_RESTRICT_SELF_TSYNC
 .TE
 .P
 Users should use the Landlock ABI version rather than the kernel version
-- 
2.53.0

[PATCH v3 4/4] man/man2/landlock_restrict_self.2: Document ABI requirement for logging flags

[Günther Noack]

Missed this on the earlier commit; we should mention since which
Landlock version these flags are available.  Users can correlate this
with the Landlock ABI version as it can be queried through
landlock_create_ruleset(2).

Signed-off-by: Günther Noack <gnoack3000@gmail.com>
---
 man/man2/landlock_restrict_self.2 | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/man/man2/landlock_restrict_self.2 b/man/man2/landlock_restrict_self.2
index 1265ea2feb91..99288b582fea 100644
--- a/man/man2/landlock_restrict_self.2
+++ b/man/man2/landlock_restrict_self.2
@@ -134,6 +134,8 @@ It can also be used with a
 value of \-1 to mute subdomain logs
 without creating a domain.
 .P
+These flags are available since Landlock ABI version 7.
+.P
 The following flag supports policy enforcement in multithreaded processes:
 .TP
 .B LANDLOCK_RESTRICT_SELF_TSYNC
-- 
2.53.0

Re: [PATCH v3 4/4] man/man2/landlock_restrict_self.2: Document ABI requirement for logging flags

[Alejandro Colomar]

[-- Attachment #1: Type: text/plain, Size: 1281 bytes --]

Hi Günther,

On 2026-04-21T19:58:42+0200, Günther Noack wrote:
> Missed this on the earlier commit; we should mention since which
> Landlock version these flags are available.  Users can correlate this
> with the Landlock ABI version as it can be queried through
> landlock_create_ruleset(2).
> 
> Signed-off-by: Günther Noack <gnoack3000@gmail.com>

I've applied patches 1,2,3.  I've amended them significantly, and this
one doesn't apply anymore.  Would you mind rebasing and using a format
similar to the one I used when amending patch 3?


Have a lovely night!
Alex

> ---
>  man/man2/landlock_restrict_self.2 | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/man/man2/landlock_restrict_self.2 b/man/man2/landlock_restrict_self.2
> index 1265ea2feb91..99288b582fea 100644
> --- a/man/man2/landlock_restrict_self.2
> +++ b/man/man2/landlock_restrict_self.2
> @@ -134,6 +134,8 @@ It can also be used with a
>  value of \-1 to mute subdomain logs
>  without creating a domain.
>  .P
> +These flags are available since Landlock ABI version 7.
> +.P
>  The following flag supports policy enforcement in multithreaded processes:
>  .TP
>  .B LANDLOCK_RESTRICT_SELF_TSYNC
> -- 
> 2.53.0
> 

-- 
<https://www.alejandro-colomar.es>

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