[PATCH bpf-next v3 1/2] bpf, cgroup: Don't populate prog_attach_flags array when effective query

[Pu Lehui <pulehui@xxxxxxxxxxxxxxx>]

From: Pu Lehui <pulehui@xxxxxxxxxx>

Attach flags is only valid for attached progs of this layer cgroup,
but not for effective progs. For querying with EFFECTIVE flags,
exporting attach flags does not make sense. so we don't need to
populate prog_attach_flags array when effective query.

Signed-off-by: Pu Lehui <pulehui@xxxxxxxxxx>
---
 kernel/bpf/cgroup.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 00c7f864900e..45b1bc47f84e 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1020,6 +1020,7 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
 			      union bpf_attr __user *uattr)
 {
 	__u32 __user *prog_attach_flags = u64_to_user_ptr(attr->query.prog_attach_flags);
+	bool effective_query = attr->query.query_flags & BPF_F_QUERY_EFFECTIVE;
 	__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
 	enum bpf_attach_type type = attr->query.attach_type;
 	enum cgroup_bpf_attach_type from_atype, to_atype;
@@ -1030,7 +1031,8 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
 	u32 flags;
 
 	if (type == BPF_LSM_CGROUP) {
-		if (attr->query.prog_cnt && prog_ids && !prog_attach_flags)
+		if (attr->query.prog_cnt && prog_ids &&
+		    !effective_query && !prog_attach_flags)
 			return -EINVAL;
 
 		from_atype = CGROUP_LSM_START;
@@ -1045,7 +1047,7 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
 	}
 
 	for (atype = from_atype; atype <= to_atype; atype++) {
-		if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE) {
+		if (effective_query) {
 			effective = rcu_dereference_protected(cgrp->bpf.effective[atype],
 							      lockdep_is_held(&cgroup_mutex));
 			total_cnt += bpf_prog_array_length(effective);
@@ -1068,7 +1070,7 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
 	}
 
 	for (atype = from_atype; atype <= to_atype && total_cnt; atype++) {
-		if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE) {
+		if (effective_query) {
 			effective = rcu_dereference_protected(cgrp->bpf.effective[atype],
 							      lockdep_is_held(&cgroup_mutex));
 			cnt = min_t(int, bpf_prog_array_length(effective), total_cnt);
@@ -1090,15 +1092,16 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
 				if (++i == cnt)
 					break;
 			}
-		}
 
-		if (prog_attach_flags) {
-			flags = cgrp->bpf.flags[atype];
+			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;
-			prog_attach_flags += cnt;
+				for (i = 0; i < cnt; i++)
+					if (copy_to_user(prog_attach_flags + i,
+							 &flags, sizeof(flags)))
+						return -EFAULT;
+				prog_attach_flags += cnt;
+			}
 		}
 
 		prog_ids += cnt;
-- 
2.25.1