net/core/netclassid_cgroup.c

   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
  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
  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 *
  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
  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
  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
  69 static 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
  86 static 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
 102 static 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
 112 static u64 read_classid(struct cgroup_subsys_state *css, struct cftype *cft)
 113 {
 114         return css_cls_state(css)->classid;
 115 }
 116
 117 static 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
 136 static struct cftype ss_files[] = {
 137         {
 138                 .name           = "classid",
 139                 .read_u64       = read_classid,
 140                 .write_u64      = write_classid,
 141         },
 142         { }     /* terminate */
 143 };
 144
 145 struct 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 };