[PATCH bpf] bpf: fix cgroup ref leak in cgroup_bpf_inherit on out-of-memory

[Andrii Nakryiko <andriin@xxxxxx>]

There is no compensating cgroup_bpf_put() for each ancestor cgroup in
cgroup_bpf_inherit(). If compute_effective_progs returns error, those cgroups
won't be freed ever. Fix it by putting them in cleanup code path.

Fixes: e10360f815ca ("bpf: cgroup: prevent out-of-order release of cgroup bpf")
Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
---
 kernel/bpf/cgroup.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 9a500fadbef5..5220a67392fc 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -227,6 +227,9 @@ int cgroup_bpf_inherit(struct cgroup *cgrp)
 	for (i = 0; i < NR; i++)
 		bpf_prog_array_free(arrays[i]);
 
+	for (p = cgroup_parent(cgrp); p; p = cgroup_parent(p))
+		cgroup_bpf_put(p);
+
 	percpu_ref_exit(&cgrp->bpf.refcnt);
 
 	return -ENOMEM;
-- 
2.17.1