landlock: Clean up ruleset validation checks

landlock_merge_ruleset() checks for a NULL ruleset after dereferencing
it in lockdep_assert_held().  Move the assertion after the check so the
defensive path remains effective.

The mask-validation comment originated in landlock_add_fs_access_mask()
to explain that its WARN_ON_ONCE() checked a caller invariant.  It
became self-referential when this helper and its network and scope
counterparts were inlined into landlock_create_ruleset().  Restate the
invariant without naming the caller.

Keep both as defensive callee checks.  Moving the assertion preserves
the NULL check's ability to warn and return -EINVAL, while invalid masks
remain warned about and masked.

Reported-by: Günther Noack <gnoack@google.com>
Closes: https://patch.msgid.link/aobYhIt3vcs2xN0b@google.com
Closes: https://patch.msgid.link/aobasxUDQ8b7GYXl@google.com
Reviewed-by: Günther Noack <gnoack@google.com>
Link: https://patch.msgid.link/20260907103609.113325-1-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

0 files changed, 0 insertions, 0 deletions