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authorToke Høiland-Jørgensen <toke@redhat.com>2019-06-28 11:12:35 +0200
committerDaniel Borkmann <daniel@iogearbox.net>2019-06-29 01:31:09 +0200
commit0cdbb4b09a0658b72c563638d476113aadd91afb (patch)
tree5e29d398bd0fcaac393d22b98ce3f0bc48f49f05 /kernel/bpf
parent43e74c0267a35d6f5127218054b2d80c7fe801f5 (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/bpf')
-rw-r--r--kernel/bpf/devmap.c5
-rw-r--r--kernel/bpf/verifier.c7
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