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 
css_cls_state(struct cgroup_subsys_state * css)16 static 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 
task_cls_state(struct task_struct * p)21 struct 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 }
26 EXPORT_SYMBOL_GPL(task_cls_state);
27 
28 static struct cgroup_subsys_state *
cgrp_css_alloc(struct cgroup_subsys_state * parent_css)29 cgrp_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 
cgrp_css_online(struct cgroup_subsys_state * css)40 static 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 
cgrp_css_free(struct cgroup_subsys_state * css)51 static 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 
62 struct update_classid_context {
63 	u32 classid;
64 	unsigned int batch;
65 };
66 
67 #define UPDATE_CLASSID_BATCH 1000
68 
update_classid_sock(const void * v,struct file * file,unsigned int n)69 static int update_classid_sock(const void *v, struct file *file, unsigned int n)
70 {
71 	struct update_classid_context *ctx = (void *)v;
72 	struct socket *sock = sock_from_file(file);
73 
74 	if (sock)
75 		sock_cgroup_set_classid(&sock->sk->sk_cgrp_data, ctx->classid);
76 	if (--ctx->batch == 0) {
77 		ctx->batch = UPDATE_CLASSID_BATCH;
78 		return n + 1;
79 	}
80 	return 0;
81 }
82 
update_classid_task(struct task_struct * p,u32 classid)83 static void update_classid_task(struct task_struct *p, u32 classid)
84 {
85 	struct update_classid_context ctx = {
86 		.classid = classid,
87 		.batch = UPDATE_CLASSID_BATCH
88 	};
89 	unsigned int fd = 0;
90 
91 	do {
92 		task_lock(p);
93 		fd = iterate_fd(p->files, fd, update_classid_sock, &ctx);
94 		task_unlock(p);
95 		cond_resched();
96 	} while (fd);
97 }
98 
cgrp_attach(struct cgroup_taskset * tset)99 static void cgrp_attach(struct cgroup_taskset *tset)
100 {
101 	struct cgroup_subsys_state *css;
102 	struct task_struct *p;
103 
104 	cgroup_taskset_for_each(p, css, tset) {
105 		update_classid_task(p, css_cls_state(css)->classid);
106 	}
107 }
108 
read_classid(struct cgroup_subsys_state * css,struct cftype * cft)109 static u64 read_classid(struct cgroup_subsys_state *css, struct cftype *cft)
110 {
111 	return css_cls_state(css)->classid;
112 }
113 
write_classid(struct cgroup_subsys_state * css,struct cftype * cft,u64 value)114 static int write_classid(struct cgroup_subsys_state *css, struct cftype *cft,
115 			 u64 value)
116 {
117 	struct cgroup_cls_state *cs = css_cls_state(css);
118 	struct css_task_iter it;
119 	struct task_struct *p;
120 
121 	cs->classid = (u32)value;
122 
123 	css_task_iter_start(css, 0, &it);
124 	while ((p = css_task_iter_next(&it)))
125 		update_classid_task(p, cs->classid);
126 	css_task_iter_end(&it);
127 
128 	return 0;
129 }
130 
131 static struct cftype ss_files[] = {
132 	{
133 		.name		= "classid",
134 		.read_u64	= read_classid,
135 		.write_u64	= write_classid,
136 	},
137 	{ }	/* terminate */
138 };
139 
140 struct cgroup_subsys net_cls_cgrp_subsys = {
141 	.css_alloc		= cgrp_css_alloc,
142 	.css_online		= cgrp_css_online,
143 	.css_free		= cgrp_css_free,
144 	.attach			= cgrp_attach,
145 	.legacy_cftypes		= ss_files,
146 };
147