fs/proc/self.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/sched.h>
   3 #include <linux/slab.h>
   4 #include <linux/pid_namespace.h>
   5 #include "internal.h"
   6
   7 /*
   8  * /proc/self:
   9  */
  10 static const char *proc_self_get_link(struct dentry *dentry,
  11                                       struct inode *inode,
  12                                       struct delayed_call *done)
  13 {
  14         struct pid_namespace *ns = inode->i_sb->s_fs_info;
  15         pid_t tgid = task_tgid_nr_ns(current, ns);
  16         char *name;
  17
  18         /*
  19          * Not currently supported. Once we can inherit all of struct pid,
  20          * we can allow this.
  21          */
  22         if (current->flags & PF_KTHREAD)
  23                 return ERR_PTR(-EOPNOTSUPP);
  24
  25         if (!tgid)
  26                 return ERR_PTR(-ENOENT);
  27         /* 11 for max length of signed int in decimal + NULL term */
  28         name = kmalloc(12, dentry ? GFP_KERNEL : GFP_ATOMIC);
  29         if (unlikely(!name))
  30                 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
  31         sprintf(name, "%d", tgid);
  32         set_delayed_call(done, kfree_link, name);
  33         return name;
  34 }
  35
  36 static const struct inode_operations proc_self_inode_operations = {
  37         .get_link       = proc_self_get_link,
  38 };
  39
  40 static unsigned self_inum;
  41
  42 int proc_setup_self(struct super_block *s)
  43 {
  44         struct inode *root_inode = d_inode(s->s_root);
  45         struct pid_namespace *ns = s->s_fs_info;
  46         struct dentry *self;
  47
  48         inode_lock(root_inode);
  49         self = d_alloc_name(s->s_root, "self");
  50         if (self) {
  51                 struct inode *inode = new_inode(s);
  52                 if (inode) {
  53                         inode->i_ino = self_inum;
  54                         inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
  55                         inode->i_mode = S_IFLNK | S_IRWXUGO;
  56                         inode->i_uid = GLOBAL_ROOT_UID;
  57                         inode->i_gid = GLOBAL_ROOT_GID;
  58                         inode->i_op = &proc_self_inode_operations;
  59                         d_add(self, inode);
  60                 } else {
  61                         dput(self);
  62                         self = ERR_PTR(-ENOMEM);
  63                 }
  64         } else {
  65                 self = ERR_PTR(-ENOMEM);
  66         }
  67         inode_unlock(root_inode);
  68         if (IS_ERR(self)) {
  69                 pr_err("proc_fill_super: can't allocate /proc/self\n");
  70                 return PTR_ERR(self);
  71         }
  72         ns->proc_self = self;
  73         return 0;
  74 }
  75
  76 void __init proc_self_init(void)
  77 {
  78         proc_alloc_inum(&self_inum);
  79 }