1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/cache.h> 3 #include <linux/sched.h> 4 #include <linux/slab.h> 5 #include <linux/pid_namespace.h> 6 #include "internal.h" 7 8 /* 9 * /proc/self: 10 */ 11 static const char *proc_self_get_link(struct dentry *dentry, 12 struct inode *inode, 13 struct delayed_call *done) 14 { 15 struct pid_namespace *ns = proc_pid_ns(inode->i_sb); 16 pid_t tgid = task_tgid_nr_ns(current, ns); 17 char *name; 18 19 /* 20 * Not currently supported. Once we can inherit all of struct pid, 21 * we can allow this. 22 */ 23 if (current->flags & PF_KTHREAD) 24 return ERR_PTR(-EOPNOTSUPP); 25 26 if (!tgid) 27 return ERR_PTR(-ENOENT); 28 /* max length of unsigned int in decimal + NULL term */ 29 name = kmalloc(10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC); 30 if (unlikely(!name)) 31 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD); 32 sprintf(name, "%u", tgid); 33 set_delayed_call(done, kfree_link, name); 34 return name; 35 } 36 37 static const struct inode_operations proc_self_inode_operations = { 38 .get_link = proc_self_get_link, 39 }; 40 41 static unsigned self_inum __ro_after_init; 42 43 int proc_setup_self(struct super_block *s) 44 { 45 struct inode *root_inode = d_inode(s->s_root); 46 struct proc_fs_info *fs_info = proc_sb_info(s); 47 struct dentry *self; 48 int ret = -ENOMEM; 49 50 inode_lock(root_inode); 51 self = d_alloc_name(s->s_root, "self"); 52 if (self) { 53 struct inode *inode = new_inode(s); 54 if (inode) { 55 inode->i_ino = self_inum; 56 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 57 inode->i_mode = S_IFLNK | S_IRWXUGO; 58 inode->i_uid = GLOBAL_ROOT_UID; 59 inode->i_gid = GLOBAL_ROOT_GID; 60 inode->i_op = &proc_self_inode_operations; 61 d_add(self, inode); 62 ret = 0; 63 } else { 64 dput(self); 65 } 66 } 67 inode_unlock(root_inode); 68 69 if (ret) 70 pr_err("proc_fill_super: can't allocate /proc/self\n"); 71 else 72 fs_info->proc_self = self; 73 74 return ret; 75 } 76 77 void __init proc_self_init(void) 78 { 79 proc_alloc_inum(&self_inum); 80 } 81