![Sean Young](/assets/img/avatar_default.png)
If the kernel is compiled with CONFIG_CGROUP_BPF not enabled, it is not
possible to attach, detach or query IR BPF programs to /dev/lircN devices,
making them impossible to use. For embedded devices, it should be possible
to use IR decoding without cgroups or CONFIG_CGROUP_BPF enabled.
This change requires some refactoring, since bpf_prog_{attach,detach,query}
functions are now always compiled, but their code paths for cgroups need
moving out. Rather than a #ifdef CONFIG_CGROUP_BPF in kernel/bpf/syscall.c,
moving them to kernel/bpf/cgroup.c and kernel/bpf/sockmap.c does not
require #ifdefs since that is already conditionally compiled.
Fixes: f4364dcfc8
("media: rc: introduce BPF_PROG_LIRC_MODE2")
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
703 lines
18 KiB
C
703 lines
18 KiB
C
/*
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* Functions to manage eBPF programs attached to cgroups
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*
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* Copyright (c) 2016 Daniel Mack
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*
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* This file is subject to the terms and conditions of version 2 of the GNU
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* General Public License. See the file COPYING in the main directory of the
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* Linux distribution for more details.
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*/
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#include <linux/kernel.h>
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#include <linux/atomic.h>
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#include <linux/cgroup.h>
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#include <linux/slab.h>
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#include <linux/bpf.h>
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#include <linux/bpf-cgroup.h>
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#include <net/sock.h>
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DEFINE_STATIC_KEY_FALSE(cgroup_bpf_enabled_key);
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EXPORT_SYMBOL(cgroup_bpf_enabled_key);
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/**
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* cgroup_bpf_put() - put references of all bpf programs
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* @cgrp: the cgroup to modify
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*/
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void cgroup_bpf_put(struct cgroup *cgrp)
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{
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unsigned int type;
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for (type = 0; type < ARRAY_SIZE(cgrp->bpf.progs); type++) {
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struct list_head *progs = &cgrp->bpf.progs[type];
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struct bpf_prog_list *pl, *tmp;
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list_for_each_entry_safe(pl, tmp, progs, node) {
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list_del(&pl->node);
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bpf_prog_put(pl->prog);
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kfree(pl);
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static_branch_dec(&cgroup_bpf_enabled_key);
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}
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bpf_prog_array_free(cgrp->bpf.effective[type]);
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}
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}
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/* count number of elements in the list.
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* it's slow but the list cannot be long
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*/
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static u32 prog_list_length(struct list_head *head)
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{
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struct bpf_prog_list *pl;
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u32 cnt = 0;
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list_for_each_entry(pl, head, node) {
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if (!pl->prog)
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continue;
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cnt++;
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}
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return cnt;
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}
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/* if parent has non-overridable prog attached,
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* disallow attaching new programs to the descendent cgroup.
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* if parent has overridable or multi-prog, allow attaching
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*/
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static bool hierarchy_allows_attach(struct cgroup *cgrp,
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enum bpf_attach_type type,
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u32 new_flags)
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{
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struct cgroup *p;
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p = cgroup_parent(cgrp);
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if (!p)
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return true;
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do {
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u32 flags = p->bpf.flags[type];
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u32 cnt;
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if (flags & BPF_F_ALLOW_MULTI)
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return true;
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cnt = prog_list_length(&p->bpf.progs[type]);
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WARN_ON_ONCE(cnt > 1);
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if (cnt == 1)
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return !!(flags & BPF_F_ALLOW_OVERRIDE);
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p = cgroup_parent(p);
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} while (p);
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return true;
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}
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/* compute a chain of effective programs for a given cgroup:
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* start from the list of programs in this cgroup and add
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* all parent programs.
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* Note that parent's F_ALLOW_OVERRIDE-type program is yielding
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* to programs in this cgroup
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*/
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static int compute_effective_progs(struct cgroup *cgrp,
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enum bpf_attach_type type,
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struct bpf_prog_array __rcu **array)
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{
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struct bpf_prog_array __rcu *progs;
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struct bpf_prog_list *pl;
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struct cgroup *p = cgrp;
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int cnt = 0;
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/* count number of effective programs by walking parents */
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do {
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if (cnt == 0 || (p->bpf.flags[type] & BPF_F_ALLOW_MULTI))
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cnt += prog_list_length(&p->bpf.progs[type]);
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p = cgroup_parent(p);
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} while (p);
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progs = bpf_prog_array_alloc(cnt, GFP_KERNEL);
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if (!progs)
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return -ENOMEM;
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/* populate the array with effective progs */
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cnt = 0;
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p = cgrp;
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do {
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if (cnt == 0 || (p->bpf.flags[type] & BPF_F_ALLOW_MULTI))
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list_for_each_entry(pl,
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&p->bpf.progs[type], node) {
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if (!pl->prog)
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continue;
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rcu_dereference_protected(progs, 1)->
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progs[cnt++] = pl->prog;
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}
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p = cgroup_parent(p);
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} while (p);
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*array = progs;
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return 0;
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}
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static void activate_effective_progs(struct cgroup *cgrp,
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enum bpf_attach_type type,
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struct bpf_prog_array __rcu *array)
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{
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struct bpf_prog_array __rcu *old_array;
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old_array = xchg(&cgrp->bpf.effective[type], array);
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/* free prog array after grace period, since __cgroup_bpf_run_*()
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* might be still walking the array
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*/
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bpf_prog_array_free(old_array);
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}
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/**
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* cgroup_bpf_inherit() - inherit effective programs from parent
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* @cgrp: the cgroup to modify
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*/
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int cgroup_bpf_inherit(struct cgroup *cgrp)
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{
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/* has to use marco instead of const int, since compiler thinks
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* that array below is variable length
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*/
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#define NR ARRAY_SIZE(cgrp->bpf.effective)
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struct bpf_prog_array __rcu *arrays[NR] = {};
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int i;
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for (i = 0; i < NR; i++)
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INIT_LIST_HEAD(&cgrp->bpf.progs[i]);
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for (i = 0; i < NR; i++)
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if (compute_effective_progs(cgrp, i, &arrays[i]))
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goto cleanup;
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for (i = 0; i < NR; i++)
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activate_effective_progs(cgrp, i, arrays[i]);
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return 0;
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cleanup:
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for (i = 0; i < NR; i++)
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bpf_prog_array_free(arrays[i]);
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return -ENOMEM;
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}
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#define BPF_CGROUP_MAX_PROGS 64
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/**
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* __cgroup_bpf_attach() - Attach the program to a cgroup, and
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* propagate the change to descendants
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* @cgrp: The cgroup which descendants to traverse
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* @prog: A program to attach
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* @type: Type of attach operation
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*
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* Must be called with cgroup_mutex held.
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*/
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int __cgroup_bpf_attach(struct cgroup *cgrp, struct bpf_prog *prog,
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enum bpf_attach_type type, u32 flags)
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{
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struct list_head *progs = &cgrp->bpf.progs[type];
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struct bpf_prog *old_prog = NULL;
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struct cgroup_subsys_state *css;
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struct bpf_prog_list *pl;
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bool pl_was_allocated;
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int err;
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if ((flags & BPF_F_ALLOW_OVERRIDE) && (flags & BPF_F_ALLOW_MULTI))
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/* invalid combination */
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return -EINVAL;
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if (!hierarchy_allows_attach(cgrp, type, flags))
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return -EPERM;
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if (!list_empty(progs) && cgrp->bpf.flags[type] != flags)
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/* Disallow attaching non-overridable on top
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* of existing overridable in this cgroup.
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* Disallow attaching multi-prog if overridable or none
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*/
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return -EPERM;
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if (prog_list_length(progs) >= BPF_CGROUP_MAX_PROGS)
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return -E2BIG;
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if (flags & BPF_F_ALLOW_MULTI) {
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list_for_each_entry(pl, progs, node)
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if (pl->prog == prog)
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/* disallow attaching the same prog twice */
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return -EINVAL;
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pl = kmalloc(sizeof(*pl), GFP_KERNEL);
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if (!pl)
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return -ENOMEM;
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pl_was_allocated = true;
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pl->prog = prog;
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list_add_tail(&pl->node, progs);
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} else {
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if (list_empty(progs)) {
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pl = kmalloc(sizeof(*pl), GFP_KERNEL);
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if (!pl)
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return -ENOMEM;
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pl_was_allocated = true;
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list_add_tail(&pl->node, progs);
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} else {
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pl = list_first_entry(progs, typeof(*pl), node);
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old_prog = pl->prog;
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pl_was_allocated = false;
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}
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pl->prog = prog;
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}
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cgrp->bpf.flags[type] = flags;
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/* allocate and recompute effective prog arrays */
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css_for_each_descendant_pre(css, &cgrp->self) {
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struct cgroup *desc = container_of(css, struct cgroup, self);
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err = compute_effective_progs(desc, type, &desc->bpf.inactive);
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if (err)
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goto cleanup;
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}
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/* all allocations were successful. Activate all prog arrays */
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css_for_each_descendant_pre(css, &cgrp->self) {
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struct cgroup *desc = container_of(css, struct cgroup, self);
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activate_effective_progs(desc, type, desc->bpf.inactive);
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desc->bpf.inactive = NULL;
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}
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static_branch_inc(&cgroup_bpf_enabled_key);
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if (old_prog) {
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bpf_prog_put(old_prog);
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static_branch_dec(&cgroup_bpf_enabled_key);
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}
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return 0;
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cleanup:
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/* oom while computing effective. Free all computed effective arrays
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* since they were not activated
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*/
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css_for_each_descendant_pre(css, &cgrp->self) {
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struct cgroup *desc = container_of(css, struct cgroup, self);
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bpf_prog_array_free(desc->bpf.inactive);
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desc->bpf.inactive = NULL;
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}
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/* and cleanup the prog list */
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pl->prog = old_prog;
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if (pl_was_allocated) {
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list_del(&pl->node);
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kfree(pl);
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}
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return err;
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}
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/**
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* __cgroup_bpf_detach() - Detach the program from a cgroup, and
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* propagate the change to descendants
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* @cgrp: The cgroup which descendants to traverse
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* @prog: A program to detach or NULL
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* @type: Type of detach operation
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*
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* Must be called with cgroup_mutex held.
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*/
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int __cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
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enum bpf_attach_type type, u32 unused_flags)
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{
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struct list_head *progs = &cgrp->bpf.progs[type];
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u32 flags = cgrp->bpf.flags[type];
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struct bpf_prog *old_prog = NULL;
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struct cgroup_subsys_state *css;
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struct bpf_prog_list *pl;
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int err;
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if (flags & BPF_F_ALLOW_MULTI) {
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if (!prog)
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/* to detach MULTI prog the user has to specify valid FD
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* of the program to be detached
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*/
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return -EINVAL;
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} else {
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if (list_empty(progs))
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/* report error when trying to detach and nothing is attached */
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return -ENOENT;
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}
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if (flags & BPF_F_ALLOW_MULTI) {
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/* find the prog and detach it */
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list_for_each_entry(pl, progs, node) {
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if (pl->prog != prog)
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continue;
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old_prog = prog;
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/* mark it deleted, so it's ignored while
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* recomputing effective
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*/
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pl->prog = NULL;
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break;
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}
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if (!old_prog)
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return -ENOENT;
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} else {
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/* to maintain backward compatibility NONE and OVERRIDE cgroups
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* allow detaching with invalid FD (prog==NULL)
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*/
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pl = list_first_entry(progs, typeof(*pl), node);
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old_prog = pl->prog;
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pl->prog = NULL;
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}
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/* allocate and recompute effective prog arrays */
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css_for_each_descendant_pre(css, &cgrp->self) {
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struct cgroup *desc = container_of(css, struct cgroup, self);
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err = compute_effective_progs(desc, type, &desc->bpf.inactive);
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if (err)
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goto cleanup;
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}
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/* all allocations were successful. Activate all prog arrays */
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css_for_each_descendant_pre(css, &cgrp->self) {
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struct cgroup *desc = container_of(css, struct cgroup, self);
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activate_effective_progs(desc, type, desc->bpf.inactive);
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desc->bpf.inactive = NULL;
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}
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/* now can actually delete it from this cgroup list */
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list_del(&pl->node);
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kfree(pl);
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if (list_empty(progs))
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/* last program was detached, reset flags to zero */
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cgrp->bpf.flags[type] = 0;
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bpf_prog_put(old_prog);
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static_branch_dec(&cgroup_bpf_enabled_key);
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return 0;
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cleanup:
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/* oom while computing effective. Free all computed effective arrays
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* since they were not activated
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*/
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css_for_each_descendant_pre(css, &cgrp->self) {
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struct cgroup *desc = container_of(css, struct cgroup, self);
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bpf_prog_array_free(desc->bpf.inactive);
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desc->bpf.inactive = NULL;
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}
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/* and restore back old_prog */
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pl->prog = old_prog;
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return err;
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}
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/* Must be called with cgroup_mutex held to avoid races. */
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int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
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union bpf_attr __user *uattr)
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{
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__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
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enum bpf_attach_type type = attr->query.attach_type;
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struct list_head *progs = &cgrp->bpf.progs[type];
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u32 flags = cgrp->bpf.flags[type];
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int cnt, ret = 0, i;
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if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE)
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cnt = bpf_prog_array_length(cgrp->bpf.effective[type]);
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else
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cnt = prog_list_length(progs);
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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, &cnt, sizeof(cnt)))
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return -EFAULT;
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if (attr->query.prog_cnt == 0 || !prog_ids || !cnt)
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/* return early if user requested only program count + flags */
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return 0;
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if (attr->query.prog_cnt < cnt) {
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cnt = attr->query.prog_cnt;
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ret = -ENOSPC;
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}
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if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE) {
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return bpf_prog_array_copy_to_user(cgrp->bpf.effective[type],
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prog_ids, cnt);
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} else {
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struct bpf_prog_list *pl;
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u32 id;
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i = 0;
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list_for_each_entry(pl, progs, node) {
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id = pl->prog->aux->id;
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if (copy_to_user(prog_ids + i, &id, sizeof(id)))
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return -EFAULT;
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if (++i == cnt)
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break;
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}
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}
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return ret;
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}
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int cgroup_bpf_prog_attach(const union bpf_attr *attr,
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enum bpf_prog_type ptype, struct bpf_prog *prog)
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{
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struct cgroup *cgrp;
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int ret;
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cgrp = cgroup_get_from_fd(attr->target_fd);
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if (IS_ERR(cgrp))
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return PTR_ERR(cgrp);
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ret = cgroup_bpf_attach(cgrp, prog, attr->attach_type,
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attr->attach_flags);
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cgroup_put(cgrp);
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return ret;
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}
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int cgroup_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
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{
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struct bpf_prog *prog;
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struct cgroup *cgrp;
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int ret;
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cgrp = cgroup_get_from_fd(attr->target_fd);
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if (IS_ERR(cgrp))
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return PTR_ERR(cgrp);
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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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prog = NULL;
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ret = cgroup_bpf_detach(cgrp, prog, attr->attach_type, 0);
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if (prog)
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bpf_prog_put(prog);
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cgroup_put(cgrp);
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return ret;
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}
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int cgroup_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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struct cgroup *cgrp;
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int ret;
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cgrp = cgroup_get_from_fd(attr->query.target_fd);
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if (IS_ERR(cgrp))
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return PTR_ERR(cgrp);
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ret = cgroup_bpf_query(cgrp, attr, uattr);
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cgroup_put(cgrp);
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return ret;
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}
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/**
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* __cgroup_bpf_run_filter_skb() - Run a program for packet filtering
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* @sk: The socket sending or receiving traffic
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* @skb: The skb that is being sent or received
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* @type: The type of program to be exectuted
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*
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* If no socket is passed, or the socket is not of type INET or INET6,
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* this function does nothing and returns 0.
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*
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* The program type passed in via @type must be suitable for network
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* filtering. No further check is performed to assert that.
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*
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* 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_skb(struct sock *sk,
|
|
struct sk_buff *skb,
|
|
enum bpf_attach_type type)
|
|
{
|
|
unsigned int offset = skb->data - skb_network_header(skb);
|
|
struct sock *save_sk;
|
|
struct cgroup *cgrp;
|
|
int ret;
|
|
|
|
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);
|
|
save_sk = skb->sk;
|
|
skb->sk = sk;
|
|
__skb_push(skb, offset);
|
|
ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], skb,
|
|
bpf_prog_run_save_cb);
|
|
__skb_pull(skb, offset);
|
|
skb->sk = save_sk;
|
|
return ret == 1 ? 0 : -EPERM;
|
|
}
|
|
EXPORT_SYMBOL(__cgroup_bpf_run_filter_skb);
|
|
|
|
/**
|
|
* __cgroup_bpf_run_filter_sk() - Run a program on a sock
|
|
* @sk: sock structure to manipulate
|
|
* @type: The type of program to be exectuted
|
|
*
|
|
* socket is passed is expected to be of type INET or INET6.
|
|
*
|
|
* The program type passed in via @type must be suitable for sock
|
|
* 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_sk(struct sock *sk,
|
|
enum bpf_attach_type type)
|
|
{
|
|
struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
|
|
int ret;
|
|
|
|
ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], sk, BPF_PROG_RUN);
|
|
return ret == 1 ? 0 : -EPERM;
|
|
}
|
|
EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk);
|
|
|
|
/**
|
|
* __cgroup_bpf_run_filter_sock_addr() - Run a program on a sock and
|
|
* provided by user sockaddr
|
|
* @sk: sock struct that will use sockaddr
|
|
* @uaddr: sockaddr struct provided by user
|
|
* @type: The type of program to be exectuted
|
|
* @t_ctx: Pointer to attach type specific context
|
|
*
|
|
* socket is expected to be of type INET or INET6.
|
|
*
|
|
* This function will return %-EPERM if an attached program is found and
|
|
* returned value != 1 during execution. In all other cases, 0 is returned.
|
|
*/
|
|
int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
|
|
struct sockaddr *uaddr,
|
|
enum bpf_attach_type type,
|
|
void *t_ctx)
|
|
{
|
|
struct bpf_sock_addr_kern ctx = {
|
|
.sk = sk,
|
|
.uaddr = uaddr,
|
|
.t_ctx = t_ctx,
|
|
};
|
|
struct sockaddr_storage unspec;
|
|
struct cgroup *cgrp;
|
|
int ret;
|
|
|
|
/* Check socket family since not all sockets represent network
|
|
* endpoint (e.g. AF_UNIX).
|
|
*/
|
|
if (sk->sk_family != AF_INET && sk->sk_family != AF_INET6)
|
|
return 0;
|
|
|
|
if (!ctx.uaddr) {
|
|
memset(&unspec, 0, sizeof(unspec));
|
|
ctx.uaddr = (struct sockaddr *)&unspec;
|
|
}
|
|
|
|
cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
|
|
ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], &ctx, BPF_PROG_RUN);
|
|
|
|
return ret == 1 ? 0 : -EPERM;
|
|
}
|
|
EXPORT_SYMBOL(__cgroup_bpf_run_filter_sock_addr);
|
|
|
|
/**
|
|
* __cgroup_bpf_run_filter_sock_ops() - Run a program on a sock
|
|
* @sk: socket to get cgroup from
|
|
* @sock_ops: bpf_sock_ops_kern struct to pass to program. Contains
|
|
* sk with connection information (IP addresses, etc.) May not contain
|
|
* cgroup info if it is a req sock.
|
|
* @type: The type of program to be exectuted
|
|
*
|
|
* socket passed is expected to be of type INET or INET6.
|
|
*
|
|
* The program type passed in via @type must be suitable for sock_ops
|
|
* 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_sock_ops(struct sock *sk,
|
|
struct bpf_sock_ops_kern *sock_ops,
|
|
enum bpf_attach_type type)
|
|
{
|
|
struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
|
|
int ret;
|
|
|
|
ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], sock_ops,
|
|
BPF_PROG_RUN);
|
|
return ret == 1 ? 0 : -EPERM;
|
|
}
|
|
EXPORT_SYMBOL(__cgroup_bpf_run_filter_sock_ops);
|
|
|
|
int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,
|
|
short access, enum bpf_attach_type type)
|
|
{
|
|
struct cgroup *cgrp;
|
|
struct bpf_cgroup_dev_ctx ctx = {
|
|
.access_type = (access << 16) | dev_type,
|
|
.major = major,
|
|
.minor = minor,
|
|
};
|
|
int allow = 1;
|
|
|
|
rcu_read_lock();
|
|
cgrp = task_dfl_cgroup(current);
|
|
allow = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], &ctx,
|
|
BPF_PROG_RUN);
|
|
rcu_read_unlock();
|
|
|
|
return !allow;
|
|
}
|
|
EXPORT_SYMBOL(__cgroup_bpf_check_dev_permission);
|
|
|
|
static const struct bpf_func_proto *
|
|
cgroup_dev_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
|
|
{
|
|
switch (func_id) {
|
|
case BPF_FUNC_map_lookup_elem:
|
|
return &bpf_map_lookup_elem_proto;
|
|
case BPF_FUNC_map_update_elem:
|
|
return &bpf_map_update_elem_proto;
|
|
case BPF_FUNC_map_delete_elem:
|
|
return &bpf_map_delete_elem_proto;
|
|
case BPF_FUNC_get_current_uid_gid:
|
|
return &bpf_get_current_uid_gid_proto;
|
|
case BPF_FUNC_trace_printk:
|
|
if (capable(CAP_SYS_ADMIN))
|
|
return bpf_get_trace_printk_proto();
|
|
default:
|
|
return NULL;
|
|
}
|
|
}
|
|
|
|
static bool cgroup_dev_is_valid_access(int off, int size,
|
|
enum bpf_access_type type,
|
|
const struct bpf_prog *prog,
|
|
struct bpf_insn_access_aux *info)
|
|
{
|
|
const int size_default = sizeof(__u32);
|
|
|
|
if (type == BPF_WRITE)
|
|
return false;
|
|
|
|
if (off < 0 || off + size > sizeof(struct bpf_cgroup_dev_ctx))
|
|
return false;
|
|
/* The verifier guarantees that size > 0. */
|
|
if (off % size != 0)
|
|
return false;
|
|
|
|
switch (off) {
|
|
case bpf_ctx_range(struct bpf_cgroup_dev_ctx, access_type):
|
|
bpf_ctx_record_field_size(info, size_default);
|
|
if (!bpf_ctx_narrow_access_ok(off, size, size_default))
|
|
return false;
|
|
break;
|
|
default:
|
|
if (size != size_default)
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
const struct bpf_prog_ops cg_dev_prog_ops = {
|
|
};
|
|
|
|
const struct bpf_verifier_ops cg_dev_verifier_ops = {
|
|
.get_func_proto = cgroup_dev_func_proto,
|
|
.is_valid_access = cgroup_dev_is_valid_access,
|
|
};
|