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From:   Roman Gushchin <guro@fb.com>
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        Roman Gushchin <guro@fb.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>
Subject: [PATCH bpf] bpf: harden flags check in cgroup_storage_update_elem()
Date:   Fri, 28 Sep 2018 14:33:21 +0100
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cgroup_storage_update_elem() shouldn't accept any flags
argument values except BPF_ANY and BPF_EXIST to guarantee
the backward compatibility, had a new flag value been added.

Fixes: de9cbbaadba5 ("bpf: introduce cgroup storage maps")
Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
---
 kernel/bpf/local_storage.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index f8746e6a9a35..2a7680106320 100644
--- a/kernel/bpf/local_storage.c
+++ b/kernel/bpf/local_storage.c
@@ -130,7 +130,7 @@ static int cgroup_storage_update_elem(struct bpf_map *map, void *_key,
 	struct bpf_cgroup_storage *storage;
 	struct bpf_storage_buffer *new;
 
-	if (flags & BPF_NOEXIST)
+	if (flags != BPF_ANY && flags != BPF_EXIST)
 		return -EINVAL;
 
 	storage = cgroup_storage_lookup((struct bpf_cgroup_storage_map *)map,
-- 
2.17.1