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

["Günther Noack" <gnoack3000@gmail.com>]

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 | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/man/man2/landlock_create_ruleset.2 b/man/man2/landlock_create_ruleset.2
index 7bca831cbd65..90d0341d2682 100644
--- a/man/man2/landlock_create_ruleset.2
+++ b/man/man2/landlock_create_ruleset.2
@@ -129,11 +129,34 @@ version.
 Unless noted otherwise,
 all features documented in these man pages are available with the
 version 1.
+.TP
+.B LANDLOCK_CREATE_RULESET_ERRATA
+If
+.I attr
+is NULL and
+.I size
+is 0, then the returned value is 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.
+The fixes generally make Landlock less restrictive or more correct,
+not more restrictive.
+.IP
+This flag is available on Linux versions where errata were fixed.
 .SH RETURN VALUE
 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 .
 On error,
-- 
2.53.0