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https://github.com/edk2-porting/linux-next.git
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73b11c2ab0
Add LINK_DETACH command to force-detach bpf_link without destroying it. It has the same behavior as auto-detaching of bpf_link due to cgroup dying for bpf_cgroup_link or net_device being destroyed for bpf_xdp_link. In such case, bpf_link is still a valid kernel object, but is defuncts and doesn't hold BPF program attached to corresponding BPF hook. This functionality allows users with enough access rights to manually force-detach attached bpf_link without killing respective owner process. This patch implements LINK_DETACH for cgroup, xdp, and netns links, mostly re-using existing link release handling code. Signed-off-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Acked-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20200731182830.286260-2-andriin@fb.com
567 lines
13 KiB
C
567 lines
13 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/bpf.h>
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#include <linux/filter.h>
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#include <net/net_namespace.h>
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/*
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* Functions to manage BPF programs attached to netns
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*/
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struct bpf_netns_link {
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struct bpf_link link;
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enum bpf_attach_type type;
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enum netns_bpf_attach_type netns_type;
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/* We don't hold a ref to net in order to auto-detach the link
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* when netns is going away. Instead we rely on pernet
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* pre_exit callback to clear this pointer. Must be accessed
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* with netns_bpf_mutex held.
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*/
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struct net *net;
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struct list_head node; /* node in list of links attached to net */
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};
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/* Protects updates to netns_bpf */
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DEFINE_MUTEX(netns_bpf_mutex);
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static void netns_bpf_attach_type_unneed(enum netns_bpf_attach_type type)
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{
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switch (type) {
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#ifdef CONFIG_INET
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case NETNS_BPF_SK_LOOKUP:
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static_branch_dec(&bpf_sk_lookup_enabled);
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break;
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#endif
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default:
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break;
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}
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}
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static void netns_bpf_attach_type_need(enum netns_bpf_attach_type type)
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{
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switch (type) {
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#ifdef CONFIG_INET
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case NETNS_BPF_SK_LOOKUP:
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static_branch_inc(&bpf_sk_lookup_enabled);
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break;
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#endif
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default:
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break;
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}
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}
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/* Must be called with netns_bpf_mutex held. */
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static void netns_bpf_run_array_detach(struct net *net,
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enum netns_bpf_attach_type type)
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{
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struct bpf_prog_array *run_array;
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run_array = rcu_replace_pointer(net->bpf.run_array[type], NULL,
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lockdep_is_held(&netns_bpf_mutex));
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bpf_prog_array_free(run_array);
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}
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static int link_index(struct net *net, enum netns_bpf_attach_type type,
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struct bpf_netns_link *link)
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{
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struct bpf_netns_link *pos;
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int i = 0;
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list_for_each_entry(pos, &net->bpf.links[type], node) {
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if (pos == link)
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return i;
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i++;
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}
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return -ENOENT;
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}
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static int link_count(struct net *net, enum netns_bpf_attach_type type)
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{
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struct list_head *pos;
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int i = 0;
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list_for_each(pos, &net->bpf.links[type])
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i++;
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return i;
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}
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static void fill_prog_array(struct net *net, enum netns_bpf_attach_type type,
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struct bpf_prog_array *prog_array)
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{
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struct bpf_netns_link *pos;
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unsigned int i = 0;
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list_for_each_entry(pos, &net->bpf.links[type], node) {
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prog_array->items[i].prog = pos->link.prog;
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i++;
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}
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}
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static void bpf_netns_link_release(struct bpf_link *link)
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{
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struct bpf_netns_link *net_link =
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container_of(link, struct bpf_netns_link, link);
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enum netns_bpf_attach_type type = net_link->netns_type;
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struct bpf_prog_array *old_array, *new_array;
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struct net *net;
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int cnt, idx;
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mutex_lock(&netns_bpf_mutex);
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/* We can race with cleanup_net, but if we see a non-NULL
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* struct net pointer, pre_exit has not run yet and wait for
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* netns_bpf_mutex.
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*/
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net = net_link->net;
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if (!net)
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goto out_unlock;
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/* Mark attach point as unused */
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netns_bpf_attach_type_unneed(type);
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/* Remember link position in case of safe delete */
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idx = link_index(net, type, net_link);
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list_del(&net_link->node);
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cnt = link_count(net, type);
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if (!cnt) {
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netns_bpf_run_array_detach(net, type);
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goto out_unlock;
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}
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old_array = rcu_dereference_protected(net->bpf.run_array[type],
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lockdep_is_held(&netns_bpf_mutex));
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new_array = bpf_prog_array_alloc(cnt, GFP_KERNEL);
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if (!new_array) {
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WARN_ON(bpf_prog_array_delete_safe_at(old_array, idx));
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goto out_unlock;
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}
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fill_prog_array(net, type, new_array);
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rcu_assign_pointer(net->bpf.run_array[type], new_array);
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bpf_prog_array_free(old_array);
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out_unlock:
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net_link->net = NULL;
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mutex_unlock(&netns_bpf_mutex);
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}
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static int bpf_netns_link_detach(struct bpf_link *link)
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{
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bpf_netns_link_release(link);
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return 0;
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}
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static void bpf_netns_link_dealloc(struct bpf_link *link)
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{
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struct bpf_netns_link *net_link =
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container_of(link, struct bpf_netns_link, link);
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kfree(net_link);
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}
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static int bpf_netns_link_update_prog(struct bpf_link *link,
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struct bpf_prog *new_prog,
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struct bpf_prog *old_prog)
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{
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struct bpf_netns_link *net_link =
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container_of(link, struct bpf_netns_link, link);
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enum netns_bpf_attach_type type = net_link->netns_type;
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struct bpf_prog_array *run_array;
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struct net *net;
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int idx, ret;
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if (old_prog && old_prog != link->prog)
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return -EPERM;
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if (new_prog->type != link->prog->type)
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return -EINVAL;
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mutex_lock(&netns_bpf_mutex);
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net = net_link->net;
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if (!net || !check_net(net)) {
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/* Link auto-detached or netns dying */
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ret = -ENOLINK;
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goto out_unlock;
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}
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run_array = rcu_dereference_protected(net->bpf.run_array[type],
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lockdep_is_held(&netns_bpf_mutex));
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idx = link_index(net, type, net_link);
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ret = bpf_prog_array_update_at(run_array, idx, new_prog);
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if (ret)
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goto out_unlock;
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old_prog = xchg(&link->prog, new_prog);
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bpf_prog_put(old_prog);
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out_unlock:
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mutex_unlock(&netns_bpf_mutex);
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return ret;
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}
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static int bpf_netns_link_fill_info(const struct bpf_link *link,
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struct bpf_link_info *info)
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{
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const struct bpf_netns_link *net_link =
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container_of(link, struct bpf_netns_link, link);
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unsigned int inum = 0;
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struct net *net;
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mutex_lock(&netns_bpf_mutex);
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net = net_link->net;
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if (net && check_net(net))
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inum = net->ns.inum;
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mutex_unlock(&netns_bpf_mutex);
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info->netns.netns_ino = inum;
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info->netns.attach_type = net_link->type;
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return 0;
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}
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static void bpf_netns_link_show_fdinfo(const struct bpf_link *link,
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struct seq_file *seq)
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{
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struct bpf_link_info info = {};
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bpf_netns_link_fill_info(link, &info);
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seq_printf(seq,
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"netns_ino:\t%u\n"
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"attach_type:\t%u\n",
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info.netns.netns_ino,
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info.netns.attach_type);
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}
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static const struct bpf_link_ops bpf_netns_link_ops = {
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.release = bpf_netns_link_release,
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.dealloc = bpf_netns_link_dealloc,
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.detach = bpf_netns_link_detach,
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.update_prog = bpf_netns_link_update_prog,
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.fill_link_info = bpf_netns_link_fill_info,
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.show_fdinfo = bpf_netns_link_show_fdinfo,
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};
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/* Must be called with netns_bpf_mutex held. */
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static int __netns_bpf_prog_query(const union bpf_attr *attr,
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union bpf_attr __user *uattr,
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struct net *net,
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enum netns_bpf_attach_type type)
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{
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__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
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struct bpf_prog_array *run_array;
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u32 prog_cnt = 0, flags = 0;
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run_array = rcu_dereference_protected(net->bpf.run_array[type],
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lockdep_is_held(&netns_bpf_mutex));
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if (run_array)
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prog_cnt = bpf_prog_array_length(run_array);
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if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)))
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return -EFAULT;
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if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt)))
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return -EFAULT;
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if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
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return 0;
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return bpf_prog_array_copy_to_user(run_array, prog_ids,
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attr->query.prog_cnt);
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}
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int netns_bpf_prog_query(const union bpf_attr *attr,
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union bpf_attr __user *uattr)
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{
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enum netns_bpf_attach_type type;
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struct net *net;
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int ret;
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if (attr->query.query_flags)
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return -EINVAL;
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type = to_netns_bpf_attach_type(attr->query.attach_type);
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if (type < 0)
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return -EINVAL;
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net = get_net_ns_by_fd(attr->query.target_fd);
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if (IS_ERR(net))
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return PTR_ERR(net);
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mutex_lock(&netns_bpf_mutex);
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ret = __netns_bpf_prog_query(attr, uattr, net, type);
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mutex_unlock(&netns_bpf_mutex);
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put_net(net);
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return ret;
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}
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int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
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{
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struct bpf_prog_array *run_array;
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enum netns_bpf_attach_type type;
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struct bpf_prog *attached;
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struct net *net;
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int ret;
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if (attr->target_fd || attr->attach_flags || attr->replace_bpf_fd)
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return -EINVAL;
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type = to_netns_bpf_attach_type(attr->attach_type);
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if (type < 0)
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return -EINVAL;
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net = current->nsproxy->net_ns;
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mutex_lock(&netns_bpf_mutex);
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/* Attaching prog directly is not compatible with links */
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if (!list_empty(&net->bpf.links[type])) {
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ret = -EEXIST;
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goto out_unlock;
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}
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switch (type) {
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case NETNS_BPF_FLOW_DISSECTOR:
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ret = flow_dissector_bpf_prog_attach_check(net, prog);
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break;
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default:
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ret = -EINVAL;
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break;
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}
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if (ret)
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goto out_unlock;
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attached = net->bpf.progs[type];
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if (attached == prog) {
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/* The same program cannot be attached twice */
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ret = -EINVAL;
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goto out_unlock;
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}
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run_array = rcu_dereference_protected(net->bpf.run_array[type],
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lockdep_is_held(&netns_bpf_mutex));
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if (run_array) {
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WRITE_ONCE(run_array->items[0].prog, prog);
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} else {
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run_array = bpf_prog_array_alloc(1, GFP_KERNEL);
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if (!run_array) {
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ret = -ENOMEM;
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goto out_unlock;
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}
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run_array->items[0].prog = prog;
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rcu_assign_pointer(net->bpf.run_array[type], run_array);
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}
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net->bpf.progs[type] = prog;
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if (attached)
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bpf_prog_put(attached);
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out_unlock:
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mutex_unlock(&netns_bpf_mutex);
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return ret;
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}
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/* Must be called with netns_bpf_mutex held. */
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static int __netns_bpf_prog_detach(struct net *net,
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enum netns_bpf_attach_type type,
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struct bpf_prog *old)
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{
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struct bpf_prog *attached;
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/* Progs attached via links cannot be detached */
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if (!list_empty(&net->bpf.links[type]))
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return -EINVAL;
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attached = net->bpf.progs[type];
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if (!attached || attached != old)
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return -ENOENT;
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netns_bpf_run_array_detach(net, type);
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net->bpf.progs[type] = NULL;
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bpf_prog_put(attached);
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return 0;
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}
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int netns_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
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{
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enum netns_bpf_attach_type type;
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struct bpf_prog *prog;
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int ret;
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if (attr->target_fd)
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return -EINVAL;
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type = to_netns_bpf_attach_type(attr->attach_type);
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if (type < 0)
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return -EINVAL;
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prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
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if (IS_ERR(prog))
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return PTR_ERR(prog);
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mutex_lock(&netns_bpf_mutex);
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ret = __netns_bpf_prog_detach(current->nsproxy->net_ns, type, prog);
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mutex_unlock(&netns_bpf_mutex);
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bpf_prog_put(prog);
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return ret;
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}
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static int netns_bpf_max_progs(enum netns_bpf_attach_type type)
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{
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switch (type) {
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case NETNS_BPF_FLOW_DISSECTOR:
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return 1;
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case NETNS_BPF_SK_LOOKUP:
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return 64;
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default:
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return 0;
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}
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}
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static int netns_bpf_link_attach(struct net *net, struct bpf_link *link,
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enum netns_bpf_attach_type type)
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{
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struct bpf_netns_link *net_link =
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container_of(link, struct bpf_netns_link, link);
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struct bpf_prog_array *run_array;
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int cnt, err;
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mutex_lock(&netns_bpf_mutex);
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cnt = link_count(net, type);
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if (cnt >= netns_bpf_max_progs(type)) {
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err = -E2BIG;
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goto out_unlock;
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}
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/* Links are not compatible with attaching prog directly */
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if (net->bpf.progs[type]) {
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err = -EEXIST;
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goto out_unlock;
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}
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switch (type) {
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case NETNS_BPF_FLOW_DISSECTOR:
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err = flow_dissector_bpf_prog_attach_check(net, link->prog);
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break;
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case NETNS_BPF_SK_LOOKUP:
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err = 0; /* nothing to check */
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break;
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default:
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err = -EINVAL;
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break;
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}
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if (err)
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goto out_unlock;
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run_array = bpf_prog_array_alloc(cnt + 1, GFP_KERNEL);
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if (!run_array) {
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err = -ENOMEM;
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goto out_unlock;
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}
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list_add_tail(&net_link->node, &net->bpf.links[type]);
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fill_prog_array(net, type, run_array);
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run_array = rcu_replace_pointer(net->bpf.run_array[type], run_array,
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lockdep_is_held(&netns_bpf_mutex));
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bpf_prog_array_free(run_array);
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/* Mark attach point as used */
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netns_bpf_attach_type_need(type);
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out_unlock:
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mutex_unlock(&netns_bpf_mutex);
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return err;
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}
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int netns_bpf_link_create(const union bpf_attr *attr, struct bpf_prog *prog)
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{
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enum netns_bpf_attach_type netns_type;
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struct bpf_link_primer link_primer;
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struct bpf_netns_link *net_link;
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enum bpf_attach_type type;
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struct net *net;
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int err;
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if (attr->link_create.flags)
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return -EINVAL;
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type = attr->link_create.attach_type;
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netns_type = to_netns_bpf_attach_type(type);
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if (netns_type < 0)
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return -EINVAL;
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net = get_net_ns_by_fd(attr->link_create.target_fd);
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if (IS_ERR(net))
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return PTR_ERR(net);
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net_link = kzalloc(sizeof(*net_link), GFP_USER);
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if (!net_link) {
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err = -ENOMEM;
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goto out_put_net;
|
|
}
|
|
bpf_link_init(&net_link->link, BPF_LINK_TYPE_NETNS,
|
|
&bpf_netns_link_ops, prog);
|
|
net_link->net = net;
|
|
net_link->type = type;
|
|
net_link->netns_type = netns_type;
|
|
|
|
err = bpf_link_prime(&net_link->link, &link_primer);
|
|
if (err) {
|
|
kfree(net_link);
|
|
goto out_put_net;
|
|
}
|
|
|
|
err = netns_bpf_link_attach(net, &net_link->link, netns_type);
|
|
if (err) {
|
|
bpf_link_cleanup(&link_primer);
|
|
goto out_put_net;
|
|
}
|
|
|
|
put_net(net);
|
|
return bpf_link_settle(&link_primer);
|
|
|
|
out_put_net:
|
|
put_net(net);
|
|
return err;
|
|
}
|
|
|
|
static int __net_init netns_bpf_pernet_init(struct net *net)
|
|
{
|
|
int type;
|
|
|
|
for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++)
|
|
INIT_LIST_HEAD(&net->bpf.links[type]);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void __net_exit netns_bpf_pernet_pre_exit(struct net *net)
|
|
{
|
|
enum netns_bpf_attach_type type;
|
|
struct bpf_netns_link *net_link;
|
|
|
|
mutex_lock(&netns_bpf_mutex);
|
|
for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++) {
|
|
netns_bpf_run_array_detach(net, type);
|
|
list_for_each_entry(net_link, &net->bpf.links[type], node) {
|
|
net_link->net = NULL; /* auto-detach link */
|
|
netns_bpf_attach_type_unneed(type);
|
|
}
|
|
if (net->bpf.progs[type])
|
|
bpf_prog_put(net->bpf.progs[type]);
|
|
}
|
|
mutex_unlock(&netns_bpf_mutex);
|
|
}
|
|
|
|
static struct pernet_operations netns_bpf_pernet_ops __net_initdata = {
|
|
.init = netns_bpf_pernet_init,
|
|
.pre_exit = netns_bpf_pernet_pre_exit,
|
|
};
|
|
|
|
static int __init netns_bpf_init(void)
|
|
{
|
|
return register_pernet_subsys(&netns_bpf_pernet_ops);
|
|
}
|
|
|
|
subsys_initcall(netns_bpf_init);
|