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         /*
  28          * Not currently supported. Once we can inherit all of struct pid,
  29          * we can allow this.
  30          */
  31         if (current->flags & PF_KTHREAD)
  32                 return ERR_PTR(-EOPNOTSUPP);
  33
  34         if (!tgid)
  35                 return ERR_PTR(-ENOENT);
  36         /* 11 for max length of signed int in decimal + NULL term */
  37         name = kmalloc(12, GFP_KERNEL);
  38         if (!name)
  39                 return ERR_PTR(-ENOMEM);
  40         sprintf(name, "%d", tgid);
  41         return *cookie = name;
  42 }
  43
  44 static const struct inode_operations proc_self_inode_operations = {
  45         .readlink       = proc_self_readlink,
  46         .follow_link    = proc_self_follow_link,
  47         .put_link       = kfree_put_link,
  48 };
  49
  50 static unsigned self_inum;
  51
  52 int proc_setup_self(struct super_block *s)
  53 {
  54         struct inode *root_inode = d_inode(s->s_root);
  55         struct pid_namespace *ns = s->s_fs_info;
  56         struct dentry *self;
  57
  58         mutex_lock(&root_inode->i_mutex);
  59         self = d_alloc_name(s->s_root, "self");
  60         if (self) {
  61                 struct inode *inode = new_inode(s);
  62                 if (inode) {
  63                         inode->i_ino = self_inum;
  64                         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  65                         inode->i_mode = S_IFLNK | S_IRWXUGO;
  66                         inode->i_uid = GLOBAL_ROOT_UID;
  67                         inode->i_gid = GLOBAL_ROOT_GID;
  68                         inode->i_op = &proc_self_inode_operations;
  69                         d_add(self, inode);
  70                 } else {
  71                         dput(self);
  72                         self = ERR_PTR(-ENOMEM);
  73                 }
  74         } else {
  75                 self = ERR_PTR(-ENOMEM);
  76         }
  77         mutex_unlock(&root_inode->i_mutex);
  78         if (IS_ERR(self)) {
  79                 pr_err("proc_fill_super: can't allocate /proc/self\n");
  80                 return PTR_ERR(self);
  81         }
  82         ns->proc_self = self;
  83         return 0;
  84 }
  85
  86 void __init proc_self_init(void)
  87 {
  88         proc_alloc_inum(&self_inum);
  89 }