[PATCH bpf] bpf: don't accept cgroup local storage with zero value size

[Roman Gushchin]

Explicitly forbid creating cgroup local storage maps with zero value
size, as it makes no sense and might even cause a panic.

Reported-by: syzbot+18628320d3b14a5c459c@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Roman Gushchin <guro@xxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
---
 kernel/bpf/local_storage.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index 944eb297465f..9f79956bff7d 100644
--- a/kernel/bpf/local_storage.c
+++ b/kernel/bpf/local_storage.c
@@ -261,6 +261,9 @@ static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
 	if (attr->key_size != sizeof(struct bpf_cgroup_storage_key))
 		return ERR_PTR(-EINVAL);
 
+	if (attr->value_size == 0)
+		return ERR_PTR(-EINVAL);
+
 	if (attr->value_size > PAGE_SIZE)
 		return ERR_PTR(-E2BIG);
 
-- 
2.17.1