Extend direct cgroup program queries to merge (pl->flags & BPF_F_PREORDER) with the cgroup-wide flags when copying prog_attach_flags to user space. Only BPF_F_PREORDER is extracted from pl->flags to ensure transient positioning flags (such as BPF_F_BEFORE, BPF_F_AFTER, BPF_F_ID, or BPF_F_REPLACE) are not leaked to user space.
This can introduce new prog_attach_flags[] values with BPF_F_PREORDER set, for example 0x40 (BPF_F_PREORDER), 0x41 (BPF_F_ALLOW_OVERRIDE | BPF_F_PREORDER), or 0x42 (BPF_F_ALLOW_MULTI | BPF_F_PREORDER), depending on the cgroup-wide attachment mode. Older bpftool versions treat such combinations as unknown flags; bpftool support is updated later in this series. Signed-off-by: Hui Su <[email protected]> --- Notes (bpf-preorder-v3-20260922-check): Testing: - PASS: ./test_progs -t cgroup_mprog_opts (x86_64 QEMU/KVM). - Result reused after a content-equivalent rebase; the patch diff is unchanged. kernel/bpf/cgroup.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 1cb5e6a6ffc1..2bbe77de89f0 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -1515,19 +1515,19 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr, id = prog_list_id(pl); if (copy_to_user(prog_ids + i, &id, sizeof(id))) return -EFAULT; + if (prog_attach_flags) { + flags = cgrp->bpf.flags[atype] | + (pl->flags & BPF_F_PREORDER); + if (copy_to_user(prog_attach_flags + i, + &flags, sizeof(flags))) + return -EFAULT; + } if (++i == cnt) break; } - if (prog_attach_flags) { - flags = cgrp->bpf.flags[atype]; - - for (i = 0; i < cnt; i++) - if (copy_to_user(prog_attach_flags + i, - &flags, sizeof(flags))) - return -EFAULT; + if (prog_attach_flags) prog_attach_flags += cnt; - } } prog_ids += cnt; -- 2.55.0
