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, void **cookie) 23 { 24 struct pid_namespace *ns = inode->i_sb->s_fs_info; 25 pid_t tgid = task_tgid_nr_ns(current, ns); 26 char *name; 27 28 if (!tgid) 29 return ERR_PTR(-ENOENT); 30 /* 11 for max length of signed int in decimal + NULL term */ 31 name = kmalloc(12, dentry ? GFP_KERNEL : GFP_ATOMIC); 32 if (unlikely(!name)) 33 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD); 34 sprintf(name, "%d", tgid); 35 return *cookie = name; 36 } 37 38 static const struct inode_operations proc_self_inode_operations = { 39 .readlink = proc_self_readlink, 40 .get_link = proc_self_get_link, 41 .put_link = kfree_put_link, 42 }; 43 44 static unsigned self_inum; 45 46 int proc_setup_self(struct super_block *s) 47 { 48 struct inode *root_inode = d_inode(s->s_root); 49 struct pid_namespace *ns = s->s_fs_info; 50 struct dentry *self; 51 52 mutex_lock(&root_inode->i_mutex); 53 self = d_alloc_name(s->s_root, "self"); 54 if (self) { 55 struct inode *inode = new_inode_pseudo(s); 56 if (inode) { 57 inode->i_ino = self_inum; 58 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; 59 inode->i_mode = S_IFLNK | S_IRWXUGO; 60 inode->i_uid = GLOBAL_ROOT_UID; 61 inode->i_gid = GLOBAL_ROOT_GID; 62 inode->i_op = &proc_self_inode_operations; 63 d_add(self, inode); 64 } else { 65 dput(self); 66 self = ERR_PTR(-ENOMEM); 67 } 68 } else { 69 self = ERR_PTR(-ENOMEM); 70 } 71 mutex_unlock(&root_inode->i_mutex); 72 if (IS_ERR(self)) { 73 pr_err("proc_fill_super: can't allocate /proc/self\n"); 74 return PTR_ERR(self); 75 } 76 ns->proc_self = self; 77 return 0; 78 } 79 80 void __init proc_self_init(void) 81 { 82 proc_alloc_inum(&self_inum); 83 } 84