kernel/fs/proc/self.c

   1 #include <linux/sched.h>
   2 #include <linux/namei.h>
   3 #include <linux/slab.h>
   4 #include <linux/pid_namespace.h>
   5 #include "internal.h"
   6
   7 /*
   8  * /proc/self:
   9  */
  10 static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
  11                               int buflen)
  12 {
  13         struct pid_namespace *ns = dentry->d_sb->s_fs_info;
  14         pid_t tgid = task_tgid_nr_ns(current, ns);
  15         char tmp[PROC_NUMBUF];
  16         if (!tgid)
  17                 return -ENOENT;
  18         sprintf(tmp, "%d", tgid);
  19         return readlink_copy(buffer, buflen, tmp);
  20 }
  21
  22 static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd)
  23 {
  24         struct pid_namespace *ns = dentry->d_sb->s_fs_info;
  25         pid_t tgid = task_tgid_nr_ns(current, ns);
  26         char *name = ERR_PTR(-ENOENT);
  27         if (tgid) {
  28                 /* 11 for max length of signed int in decimal + NULL term */
  29                 name = kmalloc(12, GFP_KERNEL);
  30                 if (!name)
  31                         name = ERR_PTR(-ENOMEM);
  32                 else
  33                         sprintf(name, "%d", tgid);
  34         }
  35         nd_set_link(nd, name);
  36         return NULL;
  37 }
  38
  39 static const struct inode_operations proc_self_inode_operations = {
  40         .readlink       = proc_self_readlink,
  41         .follow_link    = proc_self_follow_link,
  42         .put_link       = kfree_put_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         mutex_lock(&root_inode->i_mutex);
  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         mutex_unlock(&root_inode->i_mutex);
  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 }