From: Martin KaFai Lau <martin.lau@kernel.org>

effective_prog_pos(), called from replace_effective_prog() and
purge_effective_progs(), tests "!prog_list_prog(pl)" to skip a
'detaching' pl.

When detaching a pl, pl->prog and pl->link are set to NULL in case
the update_effective_progs() failed.

However, replace_effective_prog() is not detaching a pl,
so the case "!prog_list_prog()" will not happen.

In purge_effective_prog(), the pl->prog and pl->link are restored
before calling purge_effective_progs(), so the case "!prog_list_prog()"
will not happen either.

This patch removes them as a prep work for the upcoming work
in attaching struct_ops to cgroup. When attaching a struct_ops
to cgroup, there is a link->map case and the prog_list_prog()
will not consider the link->map. The replace_effective_prog()
and purge_effective_progs() will then incorrectly skip a pl
with struct_ops map attached to it.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Amery Hung <redacted>
---
 kernel/bpf/cgroup.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 4355ccb78a9c..b64f6757096c 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c

@@ -965,9 +965,10 @@ static int effective_prog_pos(struct cgroup *cgrp,
 
 		init_bstart = bstart;
 		hlist_for_each_entry(pl, &p->bpf.progs[atype], node) {
-			if (!prog_list_prog(pl))
-				continue;
-
+			/*
+			 * No detaching pl (NULL prog and link) is visible to the callers,
+			 * so skip the check compute_effective_progs() needs.
+			 */
 			if (pl->flags & BPF_F_PREORDER) {
 				if (pl == target_pl)
 					pos = bstart;

-- 
2.53.0-Meta