[PATCH bpf-next v2 1/2] bpf, cgroup: Fix attach flags being assigned to effective progs

[Pu Lehui]

From: Pu Lehui <pulehui@xxxxxxxxxx>

When root-cgroup attach multi progs and sub-cgroup attach a override
prog, query sub-cgroup with effective flags will incorrectly fill
the prog_attach_flags array. Attach flags is only valid for attached
progs of this layer cgroup, but not for effective progs. We know that
the attached progs is at the beginning of the effective progs array,
so we can just populate the elements in front of the prog_attach_flags
array.

Signed-off-by: Pu Lehui <pulehui@xxxxxxxxxx>
---
 kernel/bpf/cgroup.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 00c7f864900e..9c439d163a0b 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1093,11 +1093,14 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
 		}
 
 		if (prog_attach_flags) {
+			int progs_cnt = min_t(int, prog_list_length(&cgrp->bpf.progs[atype]), total_cnt);
 			flags = cgrp->bpf.flags[atype];
 
-			for (i = 0; i < cnt; i++)
+			/* attach flags only valid for attached progs, but not effective progs */
+			for (i = 0; i < progs_cnt; i++)
 				if (copy_to_user(prog_attach_flags + i, &flags, sizeof(flags)))
 					return -EFAULT;
+
 			prog_attach_flags += cnt;
 		}
 
-- 
2.25.1