From: Tejun Heo Date: Wed, 29 Apr 2026 18:09:11 +0000 (-1000) Subject: sched_ext: Forbid cpu-form kfuncs from cid-form schedulers X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=67edfa9eefe693bcc48e615241a89240006551ce;p=thirdparty%2Flinux.git sched_ext: Forbid cpu-form kfuncs from cid-form schedulers cid and cpu are both small s32s, trivially confused when a cid-form scheduler calls a cpu-keyed kfunc. Reject cid-form programs that reference any kfunc in the new scx_kfunc_ids_cpu_only at verifier load time. The reverse direction is intentionally permissive: cpu-form schedulers can freely call cid-form kfuncs to ease a gradual cpumask -> cid migration. The check sits in scx_kfunc_context_filter() right after the SCX struct_ops gate and before the any/idle allow and per-op allow-list checks, so it catches cpu-only kfuncs regardless of which set they belong to (any, idle, or select_cpu). v2: Sync per-entry kfunc flags with their primary declarations (Zhao). pahole intersects flags across BTF_ID_FLAGS() occurrences, so omitting them drops the flags globally. Signed-off-by: Tejun Heo Reviewed-by: Cheng-Yang Chou Reviewed-by: Zhao Mengmeng Reviewed-by: Changwoo Min Reviewed-by: Andrea Righi --- diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 79565fabd9b49..65a00c9796915 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -10121,6 +10121,47 @@ static const struct btf_kfunc_id_set scx_kfunc_set_any = { .filter = scx_kfunc_context_filter, }; +/* + * cpu-form kfuncs that are forbidden from cid-form schedulers + * (bpf_sched_ext_ops_cid). Programs targeting the cid struct_ops type must + * use the cid-form alternative (cid/cmask kfuncs). + * + * Membership overlaps with scx_kfunc_ids_{any,idle,select_cpu}; the filter + * tests this set independently and rejects matches before the per-op + * allow-list check runs. + * + * pahole/resolve_btfids scans every BTF_ID_FLAGS() at build time and + * intersects flags across duplicate entries, so each entry must carry the + * same flags as the kfunc's primary declaration; otherwise the flags get + * dropped globally. + */ +BTF_KFUNCS_START(scx_kfunc_ids_cpu_only) +BTF_ID_FLAGS(func, scx_bpf_kick_cpu, KF_IMPLICIT_ARGS) +BTF_ID_FLAGS(func, scx_bpf_task_cpu, KF_RCU) +BTF_ID_FLAGS(func, scx_bpf_cpu_rq, KF_IMPLICIT_ARGS) +BTF_ID_FLAGS(func, scx_bpf_cpu_curr, KF_IMPLICIT_ARGS | KF_RET_NULL | KF_RCU_PROTECTED) +BTF_ID_FLAGS(func, scx_bpf_cpu_node, KF_IMPLICIT_ARGS) +BTF_ID_FLAGS(func, scx_bpf_cpuperf_cap, KF_IMPLICIT_ARGS) +BTF_ID_FLAGS(func, scx_bpf_cpuperf_cur, KF_IMPLICIT_ARGS) +BTF_ID_FLAGS(func, scx_bpf_cpuperf_set, KF_IMPLICIT_ARGS) +BTF_ID_FLAGS(func, scx_bpf_get_possible_cpumask, KF_ACQUIRE) +BTF_ID_FLAGS(func, scx_bpf_get_online_cpumask, KF_ACQUIRE) +BTF_ID_FLAGS(func, scx_bpf_put_cpumask, KF_RELEASE) +BTF_ID_FLAGS(func, scx_bpf_select_cpu_dfl, KF_IMPLICIT_ARGS | KF_RCU) +BTF_ID_FLAGS(func, __scx_bpf_select_cpu_and, KF_IMPLICIT_ARGS | KF_RCU) +BTF_ID_FLAGS(func, scx_bpf_select_cpu_and, KF_RCU) +BTF_ID_FLAGS(func, scx_bpf_get_idle_cpumask, KF_IMPLICIT_ARGS | KF_ACQUIRE) +BTF_ID_FLAGS(func, scx_bpf_get_idle_cpumask_node, KF_IMPLICIT_ARGS | KF_ACQUIRE) +BTF_ID_FLAGS(func, scx_bpf_get_idle_smtmask, KF_IMPLICIT_ARGS | KF_ACQUIRE) +BTF_ID_FLAGS(func, scx_bpf_get_idle_smtmask_node, KF_IMPLICIT_ARGS | KF_ACQUIRE) +BTF_ID_FLAGS(func, scx_bpf_put_idle_cpumask, KF_RELEASE) +BTF_ID_FLAGS(func, scx_bpf_test_and_clear_cpu_idle, KF_IMPLICIT_ARGS) +BTF_ID_FLAGS(func, scx_bpf_pick_idle_cpu, KF_IMPLICIT_ARGS | KF_RCU) +BTF_ID_FLAGS(func, scx_bpf_pick_idle_cpu_node, KF_IMPLICIT_ARGS | KF_RCU) +BTF_ID_FLAGS(func, scx_bpf_pick_any_cpu, KF_IMPLICIT_ARGS | KF_RCU) +BTF_ID_FLAGS(func, scx_bpf_pick_any_cpu_node, KF_IMPLICIT_ARGS | KF_RCU) +BTF_KFUNCS_END(scx_kfunc_ids_cpu_only) + /* * Per-op kfunc allow flags. Each bit corresponds to a context-sensitive kfunc * group; an op may permit zero or more groups, with the union expressed in @@ -10184,6 +10225,7 @@ int scx_kfunc_context_filter(const struct bpf_prog *prog, u32 kfunc_id) bool in_cpu_release = btf_id_set8_contains(&scx_kfunc_ids_cpu_release, kfunc_id); bool in_idle = btf_id_set8_contains(&scx_kfunc_ids_idle, kfunc_id); bool in_any = btf_id_set8_contains(&scx_kfunc_ids_any, kfunc_id); + bool in_cpu_only = btf_id_set8_contains(&scx_kfunc_ids_cpu_only, kfunc_id); u32 moff, flags; /* Not an SCX kfunc - allow. */ @@ -10221,6 +10263,15 @@ int scx_kfunc_context_filter(const struct bpf_prog *prog, u32 kfunc_id) prog->aux->st_ops != &bpf_sched_ext_ops_cid) return -EACCES; + /* + * cid-form schedulers must use cid/cmask kfuncs. cid and cpu are both + * small s32s and trivially confused, so cpu-only kfuncs are rejected at + * load time. The reverse (cpu-form calling cid-form kfuncs) is + * intentionally permissive to ease gradual cpumask -> cid migration. + */ + if (prog->aux->st_ops == &bpf_sched_ext_ops_cid && in_cpu_only) + return -EACCES; + /* SCX struct_ops: check the per-op allow list. */ if (in_any || in_idle) return 0;