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 } 85