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6887c03bf2
Add a landlock_restrict_self(2) flag to set the no_new_privs attribute of the calling thread only after enforcement of the ruleset: no_new_privs is set if and only if the call succeeds. This removes the need for a prior prctl(2) PR_SET_NO_NEW_PRIVS call and guarantees that a failed enforcement leaves the attribute unchanged. Because no_new_privs is set by the call itself, the no_new_privs / CAP_SYS_ADMIN requirement of landlock_restrict_self(2) is fulfilled by construction, and the related EPERM check is skipped. Unlike LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF, this flag always requires a valid ruleset: with a ruleset_fd of -1, such a call would be nothing more than a Landlock-flavored prctl(2) PR_SET_NO_NEW_PRIVS, and there is no valid use case for setting no_new_privs (possibly with LANDLOCK_RESTRICT_SELF_TSYNC) without also enforcing Landlock restrictions. Rejecting these calls also keeps the option of giving them a meaning later. The attribute is only set past the last point of failure, just before committing the new credentials. When combined with LANDLOCK_RESTRICT_SELF_TSYNC, no_new_privs is set on the sibling threads as well, in their commit phase, with the same ordering. Bump the Landlock ABI version to 11, and include the minimal related test changes to keep the tests bisectable. Cc: Mickaël Salaün <mic@digikod.net> Signed-off-by: Justin Suess <utilityemal77@gmail.com> Link: https://patch.msgid.link/20260809212459.2427878-1-utilityemal77@gmail.com Signed-off-by: Mickaël Salaün <mic@digikod.net>