kernel/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_follow_link(struct dentry *dentry, void **cookie)
  22 {
  23         struct pid_namespace *ns = dentry->d_sb->s_fs_info;
  24         pid_t tgid = task_tgid_nr_ns(current, ns);
  25         char *name;
  26
  27         if (!tgid)
  28                 return ERR_PTR(-ENOENT);
  29         /* 11 for max length of signed int in decimal + NULL term */
  30         name = kmalloc(12, GFP_KERNEL);
  31         if (!name)
  32                 return ERR_PTR(-ENOMEM);
  33         sprintf(name, "%d", tgid);
  34         return *cookie = name;
  35 }
  36
  37 static const struct inode_operations proc_self_inode_operations = {
  38         .readlink       = proc_self_readlink,
  39         .follow_link    = proc_self_follow_link,
  40         .put_link       = kfree_put_link,
  41 };
  42
  43 static unsigned self_inum;
  44
  45 int proc_setup_self(struct super_block *s)
  46 {
  47         struct inode *root_inode = d_inode(s->s_root);
  48         struct pid_namespace *ns = s->s_fs_info;
  49         struct dentry *self;
  50
  51         mutex_lock(&root_inode->i_mutex);
  52         self = d_alloc_name(s->s_root, "self");
  53         if (self) {
  54                 struct inode *inode = new_inode_pseudo(s);
  55                 if (inode) {
  56                         inode->i_ino = self_inum;
  57                         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  58                         inode->i_mode = S_IFLNK | S_IRWXUGO;
  59                         inode->i_uid = GLOBAL_ROOT_UID;
  60                         inode->i_gid = GLOBAL_ROOT_GID;
  61                         inode->i_op = &proc_self_inode_operations;
  62                         d_add(self, inode);
  63                 } else {
  64                         dput(self);
  65                         self = ERR_PTR(-ENOMEM);
  66                 }
  67         } else {
  68                 self = ERR_PTR(-ENOMEM);
  69         }
  70         mutex_unlock(&root_inode->i_mutex);
  71         if (IS_ERR(self)) {
  72                 pr_err("proc_fill_super: can't allocate /proc/self\n");
  73                 return PTR_ERR(self);
  74         }
  75         ns->proc_self = self;
  76         return 0;
  77 }
  78
  79 void __init proc_self_init(void)
  80 {
  81         proc_alloc_inum(&self_inum);
  82 }