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authorDaniel Mack <daniel@zonque.org>2016-11-23 16:52:26 +0100
committerDavid S. Miller <davem@davemloft.net>2016-11-25 22:25:52 +0100
commit3007098494bec614fb55dee7bc0410bb7db5ad18 (patch)
treeff07e31da90fd790d2ae4f129d04954b70766057 /kernel/bpf/cgroup.c
parentbpf: add new prog type for cgroup socket filtering (diff)
downloadlinux-3007098494bec614fb55dee7bc0410bb7db5ad18.tar.xz
linux-3007098494bec614fb55dee7bc0410bb7db5ad18.zip
cgroup: add support for eBPF programs
This patch adds two sets of eBPF program pointers to struct cgroup. One for such that are directly pinned to a cgroup, and one for such that are effective for it. To illustrate the logic behind that, assume the following example cgroup hierarchy. A - B - C \ D - E If only B has a program attached, it will be effective for B, C, D and E. If D then attaches a program itself, that will be effective for both D and E, and the program in B will only affect B and C. Only one program of a given type is effective for a cgroup. Attaching and detaching programs will be done through the bpf(2) syscall. For now, ingress and egress inet socket filtering are the only supported use-cases. Signed-off-by: Daniel Mack <daniel@zonque.org> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/bpf/cgroup.c')
-rw-r--r--kernel/bpf/cgroup.c167
1 files changed, 167 insertions, 0 deletions
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
new file mode 100644
index 000000000000..a0ab43f264b0
--- /dev/null
+++ b/kernel/bpf/cgroup.c
@@ -0,0 +1,167 @@
+/*
+ * Functions to manage eBPF programs attached to cgroups
+ *
+ * Copyright (c) 2016 Daniel Mack
+ *
+ * This file is subject to the terms and conditions of version 2 of the GNU
+ * General Public License. See the file COPYING in the main directory of the
+ * Linux distribution for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/atomic.h>
+#include <linux/cgroup.h>
+#include <linux/slab.h>
+#include <linux/bpf.h>
+#include <linux/bpf-cgroup.h>
+#include <net/sock.h>
+
+DEFINE_STATIC_KEY_FALSE(cgroup_bpf_enabled_key);
+EXPORT_SYMBOL(cgroup_bpf_enabled_key);
+
+/**
+ * cgroup_bpf_put() - put references of all bpf programs
+ * @cgrp: the cgroup to modify
+ */
+void cgroup_bpf_put(struct cgroup *cgrp)
+{
+ unsigned int type;
+
+ for (type = 0; type < ARRAY_SIZE(cgrp->bpf.prog); type++) {
+ struct bpf_prog *prog = cgrp->bpf.prog[type];
+
+ if (prog) {
+ bpf_prog_put(prog);
+ static_branch_dec(&cgroup_bpf_enabled_key);
+ }
+ }
+}
+
+/**
+ * cgroup_bpf_inherit() - inherit effective programs from parent
+ * @cgrp: the cgroup to modify
+ * @parent: the parent to inherit from
+ */
+void cgroup_bpf_inherit(struct cgroup *cgrp, struct cgroup *parent)
+{
+ unsigned int type;
+
+ for (type = 0; type < ARRAY_SIZE(cgrp->bpf.effective); type++) {
+ struct bpf_prog *e;
+
+ e = rcu_dereference_protected(parent->bpf.effective[type],
+ lockdep_is_held(&cgroup_mutex));
+ rcu_assign_pointer(cgrp->bpf.effective[type], e);
+ }
+}
+
+/**
+ * __cgroup_bpf_update() - Update the pinned program of a cgroup, and
+ * propagate the change to descendants
+ * @cgrp: The cgroup which descendants to traverse
+ * @parent: The parent of @cgrp, or %NULL if @cgrp is the root
+ * @prog: A new program to pin
+ * @type: Type of pinning operation (ingress/egress)
+ *
+ * Each cgroup has a set of two pointers for bpf programs; one for eBPF
+ * programs it owns, and which is effective for execution.
+ *
+ * If @prog is %NULL, this function attaches a new program to the cgroup and
+ * releases the one that is currently attached, if any. @prog is then made
+ * the effective program of type @type in that cgroup.
+ *
+ * If @prog is %NULL, the currently attached program of type @type is released,
+ * and the effective program of the parent cgroup (if any) is inherited to
+ * @cgrp.
+ *
+ * Then, the descendants of @cgrp are walked and the effective program for
+ * each of them is set to the effective program of @cgrp unless the
+ * descendant has its own program attached, in which case the subbranch is
+ * skipped. This ensures that delegated subcgroups with own programs are left
+ * untouched.
+ *
+ * Must be called with cgroup_mutex held.
+ */
+void __cgroup_bpf_update(struct cgroup *cgrp,
+ struct cgroup *parent,
+ struct bpf_prog *prog,
+ enum bpf_attach_type type)
+{
+ struct bpf_prog *old_prog, *effective;
+ struct cgroup_subsys_state *pos;
+
+ old_prog = xchg(cgrp->bpf.prog + type, prog);
+
+ effective = (!prog && parent) ?
+ rcu_dereference_protected(parent->bpf.effective[type],
+ lockdep_is_held(&cgroup_mutex)) :
+ prog;
+
+ css_for_each_descendant_pre(pos, &cgrp->self) {
+ struct cgroup *desc = container_of(pos, struct cgroup, self);
+
+ /* skip the subtree if the descendant has its own program */
+ if (desc->bpf.prog[type] && desc != cgrp)
+ pos = css_rightmost_descendant(pos);
+ else
+ rcu_assign_pointer(desc->bpf.effective[type],
+ effective);
+ }
+
+ if (prog)
+ static_branch_inc(&cgroup_bpf_enabled_key);
+
+ if (old_prog) {
+ bpf_prog_put(old_prog);
+ static_branch_dec(&cgroup_bpf_enabled_key);
+ }
+}
+
+/**
+ * __cgroup_bpf_run_filter() - Run a program for packet filtering
+ * @sk: The socken sending or receiving traffic
+ * @skb: The skb that is being sent or received
+ * @type: The type of program to be exectuted
+ *
+ * If no socket is passed, or the socket is not of type INET or INET6,
+ * this function does nothing and returns 0.
+ *
+ * The program type passed in via @type must be suitable for network
+ * filtering. No further check is performed to assert that.
+ *
+ * This function will return %-EPERM if any if an attached program was found
+ * and if it returned != 1 during execution. In all other cases, 0 is returned.
+ */
+int __cgroup_bpf_run_filter(struct sock *sk,
+ struct sk_buff *skb,
+ enum bpf_attach_type type)
+{
+ struct bpf_prog *prog;
+ struct cgroup *cgrp;
+ int ret = 0;
+
+ if (!sk || !sk_fullsock(sk))
+ return 0;
+
+ if (sk->sk_family != AF_INET &&
+ sk->sk_family != AF_INET6)
+ return 0;
+
+ cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
+
+ rcu_read_lock();
+
+ prog = rcu_dereference(cgrp->bpf.effective[type]);
+ if (prog) {
+ unsigned int offset = skb->data - skb_network_header(skb);
+
+ __skb_push(skb, offset);
+ ret = bpf_prog_run_save_cb(prog, skb) == 1 ? 0 : -EPERM;
+ __skb_pull(skb, offset);
+ }
+
+ rcu_read_unlock();
+
+ return ret;
+}
+EXPORT_SYMBOL(__cgroup_bpf_run_filter);