tree 3e4214578e9df484c628290065baf95cecd3118b
parent ede95a63b5e84ddeea6b0c473b36ab8bfd8c6ce3
author Daniel Borkmann <daniel@iogearbox.net> 1540594142 +0200
committer Alexei Starovoitov <ast@kernel.org> 1540595010 -0700

bpf: fix wrong helper enablement in cgroup local storage

Commit cd3394317653 ("bpf: introduce the bpf_get_local_storage()
helper function") enabled the bpf_get_local_storage() helper also
for BPF program types where it does not make sense to use them.

They have been added both in sk_skb_func_proto() and sk_msg_func_proto()
even though both program types are not invoked in combination with
cgroups, and neither through BPF_PROG_RUN_ARRAY(). In the latter the
bpf_cgroup_storage_set() is set shortly before BPF program invocation.

Later, the helper bpf_get_local_storage() retrieves this prior set
up per-cpu pointer and hands the buffer to the BPF program. The map
argument in there solely retrieves the enum bpf_cgroup_storage_type
from a local storage map associated with the program and based on the
type returns either the global or per-cpu storage. However, there
is no specific association between the program's map and the actual
content in bpf_cgroup_storage[].

Meaning, any BPF program that would have been properly run from the
cgroup side through BPF_PROG_RUN_ARRAY() where bpf_cgroup_storage_set()
was performed, and that is later unloaded such that prog / maps are
teared down will cause a use after free if that pointer is retrieved
from programs that are not run through BPF_PROG_RUN_ARRAY() but have
the cgroup local storage helper enabled in their func proto.

Lets just remove it from the two sock_map program types to fix it.
Auditing through the types where this helper is enabled, it appears
that these are the only ones where it was mistakenly allowed.

Fixes: cd3394317653 ("bpf: introduce the bpf_get_local_storage() helper function")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Roman Gushchin <guro@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>