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bpf, cgroup: Fix cgroup struct_ops query for a second attach type

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Two things in __cgroup_bpf_query() work only because CGROUP_TCP_SOCK_OPS is
the only struct_ops attach type.

It calls cgroup_bpf_enabled(atype) with an atype that
find_atype_by_struct_ops_id() works out at runtime.  That macro is an asm
goto and needs a constant.  Today the compiler can see there is only one
value; add a second type and the build breaks with "impossible constraint
in 'asm'".  The check is not needed anyway.  When the key is off nothing is
attached, so progs[atype] and effective[atype] are empty and the count loop
leaves total_cnt at 0.  The other attach types already use that loop with
no such check.  Drop the check and the skip_count label.

And find_atype_by_struct_ops_id() matches on type_id alone.  An attach type
whose subsystem is not built keeps type_id 0, so a query for type 0 finds
it and returns success with nothing instead of -ENOENT.  Skip such slots.

Fixes: 369d9dcd8f ("bpf: Add infrastructure to support attaching struct_ops to cgroups")
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Amery Hung <ameryhung@gmail.com>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://patch.msgid.link/20261001141901.3225830-1-shakeel.butt@linux.dev
This commit is contained in:
Shakeel Butt 2026-10-01 07:19:01 -07:00 committed by Alexei Starovoitov
parent 6a75c73eeb
commit b5a4aa31ab
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1 changed files with 1 additions and 3 deletions
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4
kernel/bpf/cgroup.c
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@ -45,6 +45,7 @@ static enum cgroup_bpf_attach_type find_atype_by_struct_ops_id(u32 type_id)
for (atype = 0; atype < MAX_CGROUP_BPF_ATTACH_TYPE; atype++) {
if (cgroup_bpf_is_struct_ops_atype(atype) &&
cgroup_struct_ops[atype].type_id &&
cgroup_struct_ops[atype].type_id == type_id)
return atype;
}
@ -1448,8 +1449,6 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
return -ENOENT;
from_atype = to_atype = atype;
flags = 0;
if (!cgroup_bpf_enabled(atype))
goto skip_count;
} else if (type == BPF_LSM_CGROUP) {
if (!effective_query && attr->query.prog_cnt &&
prog_ids && !prog_attach_flags)
@ -1476,7 +1475,6 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
}
}
skip_count:
/* always output uattr->query.attach_flags as 0 during effective query */
flags = effective_query ? 0 : flags;
if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)))