diff options
| author | Jakub Sitnicki <jakub@cloudflare.com> | 2019-10-11 10:29:45 +0200 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2019-10-11 22:26:22 +0200 |
| commit | 719b78a5674f15fef2e4a56484614657fd759978 (patch) | |
| tree | 6dfbc486cd94db2fc45a75ad11d94b26d1c806ae /net/core | |
| parent | 84a081f60db63aaae3665118203506aa09a7f94f (diff) | |
flow_dissector: Allow updating the flow dissector program atomically
It is currently not possible to detach the flow dissector program and
attach a new one in an atomic fashion, that is with a single syscall.
Attempts to do so will be met with EEXIST error.
This makes updates to flow dissector program hard. Traffic steering that
relies on BPF-powered flow dissection gets disrupted while old program has
been already detached but the new one has not been attached yet.
There is also a window of opportunity to attach a flow dissector to a
non-root namespace while updating the root flow dissector, thus blocking
the update.
Lastly, the behavior is inconsistent with cgroup BPF programs, which can be
replaced with a single bpf(BPF_PROG_ATTACH, ...) syscall without any
restrictions.
Allow attaching a new flow dissector program when another one is already
present with a restriction that it can't be the same program.
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191011082946.22695-2-jakub@cloudflare.com
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/flow_dissector.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c index 6b4b88d1599d..dbf502c18656 100644 --- a/net/core/flow_dissector.c +++ b/net/core/flow_dissector.c @@ -128,6 +128,8 @@ int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr, struct net *ns; for_each_net(ns) { + if (ns == &init_net) + continue; if (rcu_access_pointer(ns->flow_dissector_prog)) { ret = -EEXIST; goto out; @@ -145,12 +147,14 @@ int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr, attached = rcu_dereference_protected(net->flow_dissector_prog, lockdep_is_held(&flow_dissector_mutex)); - if (attached) { - /* Only one BPF program can be attached at a time */ - ret = -EEXIST; + if (attached == prog) { + /* The same program cannot be attached twice */ + ret = -EINVAL; goto out; } rcu_assign_pointer(net->flow_dissector_prog, prog); + if (attached) + bpf_prog_put(attached); out: mutex_unlock(&flow_dissector_mutex); return ret; |