fs/proc/namespaces.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/proc_fs.h>
   3 #include <linux/nsproxy.h>
   4 #include <linux/ptrace.h>
   5 #include <linux/namei.h>
   6 #include <linux/file.h>
   7 #include <linux/utsname.h>
   8 #include <net/net_namespace.h>
   9 #include <linux/ipc_namespace.h>
  10 #include <linux/pid_namespace.h>
  11 #include <linux/user_namespace.h>
  12 #include "internal.h"
  13
  14
  15 static const struct proc_ns_operations *ns_entries[] = {
  16 #ifdef CONFIG_NET_NS
  17         &netns_operations,
  18 #endif
  19 #ifdef CONFIG_UTS_NS
  20         &utsns_operations,
  21 #endif
  22 #ifdef CONFIG_IPC_NS
  23         &ipcns_operations,
  24 #endif
  25 #ifdef CONFIG_PID_NS
  26         &pidns_operations,
  27         &pidns_for_children_operations,
  28 #endif
  29 #ifdef CONFIG_USER_NS
  30         &userns_operations,
  31 #endif
  32         &mntns_operations,
  33 #ifdef CONFIG_CGROUPS
  34         &cgroupns_operations,
  35 #endif
  36 };
  37
  38 static const char *proc_ns_get_link(struct dentry *dentry,
  39                                     struct inode *inode,
  40                                     struct delayed_call *done)
  41 {
  42         const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns_ops;
  43         struct task_struct *task;
  44         struct path ns_path;
  45         void *error = ERR_PTR(-EACCES);
  46
  47         if (!dentry)
  48                 return ERR_PTR(-ECHILD);
  49
  50         task = get_proc_task(inode);
  51         if (!task)
  52                 return error;
  53
  54         if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) {
  55                 error = ns_get_path(&ns_path, task, ns_ops);
  56                 if (!error)
  57                         nd_jump_link(&ns_path);
  58         }
  59         put_task_struct(task);
  60         return error;
  61 }
  62
  63 static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int buflen)
  64 {
  65         struct inode *inode = d_inode(dentry);
  66         const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns_ops;
  67         struct task_struct *task;
  68         char name[50];
  69         int res = -EACCES;
  70
  71         task = get_proc_task(inode);
  72         if (!task)
  73                 return res;
  74
  75         if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) {
  76                 res = ns_get_name(name, sizeof(name), task, ns_ops);
  77                 if (res >= 0)
  78                         res = readlink_copy(buffer, buflen, name);
  79         }
  80         put_task_struct(task);
  81         return res;
  82 }
  83
  84 static const struct inode_operations proc_ns_link_inode_operations = {
  85         .readlink       = proc_ns_readlink,
  86         .get_link       = proc_ns_get_link,
  87         .setattr        = proc_setattr,
  88 };
  89
  90 static int proc_ns_instantiate(struct inode *dir,
  91         struct dentry *dentry, struct task_struct *task, const void *ptr)
  92 {
  93         const struct proc_ns_operations *ns_ops = ptr;
  94         struct inode *inode;
  95         struct proc_inode *ei;
  96
  97         inode = proc_pid_make_inode(dir->i_sb, task, S_IFLNK | S_IRWXUGO);
  98         if (!inode)
  99                 goto out;
 100
 101         ei = PROC_I(inode);
 102         inode->i_op = &proc_ns_link_inode_operations;
 103         ei->ns_ops = ns_ops;
 104
 105         d_set_d_op(dentry, &pid_dentry_operations);
 106         d_add(dentry, inode);
 107         /* Close the race of the process dying before we return the dentry */
 108         if (pid_revalidate(dentry, 0))
 109                 return 0;
 110 out:
 111         return -ENOENT;
 112 }
 113
 114 static int proc_ns_dir_readdir(struct file *file, struct dir_context *ctx)
 115 {
 116         struct task_struct *task = get_proc_task(file_inode(file));
 117         const struct proc_ns_operations **entry, **last;
 118
 119         if (!task)
 120                 return -ENOENT;
 121
 122         if (!dir_emit_dots(file, ctx))
 123                 goto out;
 124         if (ctx->pos >= 2 + ARRAY_SIZE(ns_entries))
 125                 goto out;
 126         entry = ns_entries + (ctx->pos - 2);
 127         last = &ns_entries[ARRAY_SIZE(ns_entries) - 1];
 128         while (entry <= last) {
 129                 const struct proc_ns_operations *ops = *entry;
 130                 if (!proc_fill_cache(file, ctx, ops->name, strlen(ops->name),
 131                                      proc_ns_instantiate, task, ops))
 132                         break;
 133                 ctx->pos++;
 134                 entry++;
 135         }
 136 out:
 137         put_task_struct(task);
 138         return 0;
 139 }
 140
 141 const struct file_operations proc_ns_dir_operations = {
 142         .read           = generic_read_dir,
 143         .iterate_shared = proc_ns_dir_readdir,
 144         .llseek         = generic_file_llseek,
 145 };
 146
 147 static struct dentry *proc_ns_dir_lookup(struct inode *dir,
 148                                 struct dentry *dentry, unsigned int flags)
 149 {
 150         int error;
 151         struct task_struct *task = get_proc_task(dir);
 152         const struct proc_ns_operations **entry, **last;
 153         unsigned int len = dentry->d_name.len;
 154
 155         error = -ENOENT;
 156
 157         if (!task)
 158                 goto out_no_task;
 159
 160         last = &ns_entries[ARRAY_SIZE(ns_entries)];
 161         for (entry = ns_entries; entry < last; entry++) {
 162                 if (strlen((*entry)->name) != len)
 163                         continue;
 164                 if (!memcmp(dentry->d_name.name, (*entry)->name, len))
 165                         break;
 166         }
 167         if (entry == last)
 168                 goto out;
 169
 170         error = proc_ns_instantiate(dir, dentry, task, *entry);
 171 out:
 172         put_task_struct(task);
 173 out_no_task:
 174         return ERR_PTR(error);
 175 }
 176
 177 const struct inode_operations proc_ns_dir_inode_operations = {
 178         .lookup         = proc_ns_dir_lookup,
 179         .getattr        = pid_getattr,
 180         .setattr        = proc_setattr,
 181 };