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