fs/proc/self.c

   1 #include <linux/sched.h>
   2 #include <linux/slab.h>
   3 #include <linux/pid_namespace.h>
   4 #include "internal.h"
   5
   6 /*
   7  * /proc/self:
   8  */
   9 static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
  10                               int buflen)
  11 {
  12         struct pid_namespace *ns = dentry->d_sb->s_fs_info;
  13         pid_t tgid = task_tgid_nr_ns(current, ns);
  14         char tmp[PROC_NUMBUF];
  15         if (!tgid)
  16                 return -ENOENT;
  17         sprintf(tmp, "%d", tgid);
  18         return readlink_copy(buffer, buflen, tmp);
  19 }
  20
  21 static const char *proc_self_get_link(struct dentry *dentry,
  22                                       struct inode *inode,
  23                                       struct delayed_call *done)
  24 {
  25         struct pid_namespace *ns = inode->i_sb->s_fs_info;
  26         pid_t tgid = task_tgid_nr_ns(current, ns);
  27         char *name;
  28
  29         if (!tgid)
  30                 return ERR_PTR(-ENOENT);
  31         /* 11 for max length of signed int in decimal + NULL term */
  32         name = kmalloc(12, dentry ? GFP_KERNEL : GFP_ATOMIC);
  33         if (unlikely(!name))
  34                 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
  35         sprintf(name, "%d", tgid);
  36         set_delayed_call(done, kfree_link, name);
  37         return name;
  38 }
  39
  40 static const struct inode_operations proc_self_inode_operations = {
  41         .readlink       = proc_self_readlink,
  42         .get_link       = proc_self_get_link,
  43 };
  44
  45 static unsigned self_inum;
  46
  47 int proc_setup_self(struct super_block *s)
  48 {
  49         struct inode *root_inode = d_inode(s->s_root);
  50         struct pid_namespace *ns = s->s_fs_info;
  51         struct dentry *self;
  52
  53         inode_lock(root_inode);
  54         self = d_alloc_name(s->s_root, "self");
  55         if (self) {
  56                 struct inode *inode = new_inode_pseudo(s);
  57                 if (inode) {
  58                         inode->i_ino = self_inum;
  59                         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  60                         inode->i_mode = S_IFLNK | S_IRWXUGO;
  61                         inode->i_uid = GLOBAL_ROOT_UID;
  62                         inode->i_gid = GLOBAL_ROOT_GID;
  63                         inode->i_op = &proc_self_inode_operations;
  64                         d_add(self, inode);
  65                 } else {
  66                         dput(self);
  67                         self = ERR_PTR(-ENOMEM);
  68                 }
  69         } else {
  70                 self = ERR_PTR(-ENOMEM);
  71         }
  72         inode_unlock(root_inode);
  73         if (IS_ERR(self)) {
  74                 pr_err("proc_fill_super: can't allocate /proc/self\n");
  75                 return PTR_ERR(self);
  76         }
  77         ns->proc_self = self;
  78         return 0;
  79 }
  80
  81 void __init proc_self_init(void)
  82 {
  83         proc_alloc_inum(&self_inum);
  84 }