From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: David Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org,
Jesper Dangaard Brouer <brouer@redhat.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>
Subject: [PATCH net-next v2 2/2] devmap: Allow map lookups from eBPF
Date: Thu, 06 Jun 2019 15:24:14 +0200 [thread overview]
Message-ID: <155982745466.30088.16226777266948206538.stgit@alrua-x1> (raw)
In-Reply-To: <155982745450.30088.1132406322084580770.stgit@alrua-x1>
From: Toke Høiland-Jørgensen <toke@redhat.com>
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>
---
kernel/bpf/devmap.c | 5 +++++
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 5ae7cce5ef16..0e6875a462ef 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -99,6 +99,11 @@ 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 5c2cb5bd84ce..7128a9821481 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2893,12 +2893,9 @@ 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
next prev parent reply other threads:[~2019-06-06 13:24 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-06 13:24 [PATCH net-next v2 0/2] xdp: Allow lookup into devmaps before redirect Toke Høiland-Jørgensen
2019-06-06 13:24 ` [PATCH net-next v2 1/2] bpf_xdp_redirect_map: Add flag to return XDP_PASS on map lookup failure Toke Høiland-Jørgensen
2019-06-06 15:51 ` Daniel Borkmann
2019-06-06 15:56 ` Alexei Starovoitov
2019-06-06 16:15 ` Toke Høiland-Jørgensen
2019-06-06 18:15 ` Jonathan Lemon
2019-06-06 19:24 ` Daniel Borkmann
2019-06-06 20:13 ` Jonathan Lemon
2019-06-06 21:14 ` Toke Høiland-Jørgensen
2019-06-06 21:53 ` Jonathan Lemon
2019-06-06 22:31 ` Toke Høiland-Jørgensen
2019-06-06 13:24 ` Toke Høiland-Jørgensen [this message]
2019-06-06 13:33 ` [PATCH net-next v2 2/2] devmap: Allow map lookups from eBPF Jesper Dangaard Brouer
2019-06-06 13:49 ` Toke Høiland-Jørgensen
2019-06-06 18:20 ` [PATCH net-next v2 0/2] xdp: Allow lookup into devmaps before redirect David Miller
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