[PATCH 5.5 118/170] bpf: Fix cgroup ref leak in cgroup_bpf_inherit on out-of-memory

[Greg Kroah-Hartman]

From: Andrii Nakryiko <andriin@xxxxxx>

commit 1d8006abaab4cb90f81add86e8d1bf9411add05a upstream.

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>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Acked-by: Roman Gushchin <guro@xxxxxx>
Link: https://lore.kernel.org/bpf/20200309224017.1063297-1-andriin@xxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/bpf/cgroup.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -228,6 +228,9 @@ cleanup:
 	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;