diff options
| author | Toke Høiland-Jørgensen <toke@redhat.com> | 2019-06-28 11:12:35 +0200 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2019-06-29 01:31:09 +0200 |
| commit | 0cdbb4b09a0658b72c563638d476113aadd91afb (patch) | |
| tree | 5e29d398bd0fcaac393d22b98ce3f0bc48f49f05 /kernel | |
| parent | 43e74c0267a35d6f5127218054b2d80c7fe801f5 (diff) | |
devmap: Allow map lookups from eBPF
We don't currently allow lookups into a devmap from eBPF, because the map
lookup returns a pointer directly to the dev->ifindex, which shouldn't be
modifiable from eBPF.
However, being able to do lookups in devmaps is useful to know (e.g.)
whether forwarding to a specific interface is enabled. Currently, programs
work around this by keeping a shadow map of another type which indicates
whether a map index is valid.
Since we now have a flag to make maps read-only from the eBPF side, we can
simply lift the lookup restriction if we make sure this flag is always set.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/devmap.c | 5 | ||||
| -rw-r--r-- | kernel/bpf/verifier.c | 7 |
2 files changed, 7 insertions, 5 deletions
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c index a4dddc867cbf..d83cf8ccc872 100644 --- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c @@ -89,6 +89,11 @@ static struct bpf_map *dev_map_alloc(union bpf_attr *attr) attr->value_size != 4 || attr->map_flags & ~DEV_CREATE_FLAG_MASK) return ERR_PTR(-EINVAL); + /* Lookup returns a pointer straight to dev->ifindex, so make sure the + * verifier prevents writes from the BPF side + */ + attr->map_flags |= BPF_F_RDONLY_PROG; + dtab = kzalloc(sizeof(*dtab), GFP_USER); if (!dtab) return ERR_PTR(-ENOMEM); diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 6b5623d320f9..9b6ee93d5a85 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3414,12 +3414,9 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env, if (func_id != BPF_FUNC_get_local_storage) goto error; break; - /* devmap returns a pointer to a live net_device ifindex that we cannot - * allow to be modified from bpf side. So do not allow lookup elements - * for now. - */ case BPF_MAP_TYPE_DEVMAP: - if (func_id != BPF_FUNC_redirect_map) + if (func_id != BPF_FUNC_redirect_map && + func_id != BPF_FUNC_map_lookup_elem) goto error; break; /* Restrict bpf side of cpumap and xskmap, open when use-cases |