1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * net/core/netclassid_cgroup.c	Classid Cgroupfs Handling
  4 *
  5 * Authors:	Thomas Graf <tgraf@suug.ch>
  6 */
  7
  8#include <linux/slab.h>
  9#include <linux/cgroup.h>
 10#include <linux/fdtable.h>
 11#include <linux/sched/task.h>
 12
 13#include <net/cls_cgroup.h>
 14#include <net/sock.h>
 15
 16static inline struct cgroup_cls_state *css_cls_state(struct cgroup_subsys_state *css)
 17{
 18	return css ? container_of(css, struct cgroup_cls_state, css) : NULL;
 19}
 20
 21struct cgroup_cls_state *task_cls_state(struct task_struct *p)
 22{
 23	return css_cls_state(task_css_check(p, net_cls_cgrp_id,
 24					    rcu_read_lock_bh_held()));
 25}
 26EXPORT_SYMBOL_GPL(task_cls_state);
 27
 28static struct cgroup_subsys_state *
 29cgrp_css_alloc(struct cgroup_subsys_state *parent_css)
 30{
 31	struct cgroup_cls_state *cs;
 32
 33	cs = kzalloc(sizeof(*cs), GFP_KERNEL);
 34	if (!cs)
 35		return ERR_PTR(-ENOMEM);
 36
 37	return &cs->css;
 38}
 39
 40static int cgrp_css_online(struct cgroup_subsys_state *css)
 41{
 42	struct cgroup_cls_state *cs = css_cls_state(css);
 43	struct cgroup_cls_state *parent = css_cls_state(css->parent);
 44
 45	if (parent)
 46		cs->classid = parent->classid;
 47
 48	return 0;
 49}
 50
 51static void cgrp_css_free(struct cgroup_subsys_state *css)
 52{
 53	kfree(css_cls_state(css));
 54}
 55
 56/*
 57 * To avoid freezing of sockets creation for tasks with big number of threads
 58 * and opened sockets lets release file_lock every 1000 iterated descriptors.
 59 * New sockets will already have been created with new classid.
 60 */
 61
 62struct update_classid_context {
 63	u32 classid;
 64	unsigned int batch;
 65};
 66
 67#define UPDATE_CLASSID_BATCH 1000
 68
 69static int update_classid_sock(const void *v, struct file *file, unsigned n)
 70{
 71	struct update_classid_context *ctx = (void *)v;
 72	struct socket *sock = sock_from_file(file);
 73
 74	if (sock) {
 75		spin_lock(&cgroup_sk_update_lock);
 76		sock_cgroup_set_classid(&sock->sk->sk_cgrp_data, ctx->classid);
 77		spin_unlock(&cgroup_sk_update_lock);
 78	}
 79	if (--ctx->batch == 0) {
 80		ctx->batch = UPDATE_CLASSID_BATCH;
 81		return n + 1;
 82	}
 83	return 0;
 84}
 85
 86static void update_classid_task(struct task_struct *p, u32 classid)
 87{
 88	struct update_classid_context ctx = {
 89		.classid = classid,
 90		.batch = UPDATE_CLASSID_BATCH
 91	};
 92	unsigned int fd = 0;
 93
 94	do {
 95		task_lock(p);
 96		fd = iterate_fd(p->files, fd, update_classid_sock, &ctx);
 97		task_unlock(p);
 98		cond_resched();
 99	} while (fd);
100}
101
102static void cgrp_attach(struct cgroup_taskset *tset)
103{
104	struct cgroup_subsys_state *css;
105	struct task_struct *p;
106
107	cgroup_taskset_for_each(p, css, tset) {
108		update_classid_task(p, css_cls_state(css)->classid);
109	}
110}
111
112static u64 read_classid(struct cgroup_subsys_state *css, struct cftype *cft)
113{
114	return css_cls_state(css)->classid;
115}
116
117static int write_classid(struct cgroup_subsys_state *css, struct cftype *cft,
118			 u64 value)
119{
120	struct cgroup_cls_state *cs = css_cls_state(css);
121	struct css_task_iter it;
122	struct task_struct *p;
123
124	cgroup_sk_alloc_disable();
125
126	cs->classid = (u32)value;
127
128	css_task_iter_start(css, 0, &it);
129	while ((p = css_task_iter_next(&it)))
130		update_classid_task(p, cs->classid);
131	css_task_iter_end(&it);
132
133	return 0;
134}
135
136static struct cftype ss_files[] = {
137	{
138		.name		= "classid",
139		.read_u64	= read_classid,
140		.write_u64	= write_classid,
141	},
142	{ }	/* terminate */
143};
144
145struct cgroup_subsys net_cls_cgrp_subsys = {
146	.css_alloc		= cgrp_css_alloc,
147	.css_online		= cgrp_css_online,
148	.css_free		= cgrp_css_free,
149	.attach			= cgrp_attach,
150	.legacy_cftypes		= ss_files,
151};