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); 16 pid_t tgid = task_tgid_nr_ns(current, ns); 17 char *name; 18 19 if (!tgid) 20 return ERR_PTR(-ENOENT); 21 /* max length of unsigned int in decimal + NULL term */ 22 name = kmalloc(10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC); 23 if (unlikely(!name)) 24 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD); 25 sprintf(name, "%u", tgid); 26 set_delayed_call(done, kfree_link, name); 27 return name; 28 } 29 30 static const struct inode_operations proc_self_inode_operations = { 31 .get_link = proc_self_get_link, 32 }; 33 34 static unsigned self_inum __ro_after_init; 35 36 int proc_setup_self(struct super_block *s) 37 { 38 struct inode *root_inode = d_inode(s->s_root); 39 struct pid_namespace *ns = proc_pid_ns(root_inode); 40 struct dentry *self; 41 int ret = -ENOMEM; 42 43 inode_lock(root_inode); 44 self = d_alloc_name(s->s_root, "self"); 45 if (self) { 46 struct inode *inode = new_inode_pseudo(s); 47 if (inode) { 48 inode->i_ino = self_inum; 49 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 50 inode->i_mode = S_IFLNK | S_IRWXUGO; 51 inode->i_uid = GLOBAL_ROOT_UID; 52 inode->i_gid = GLOBAL_ROOT_GID; 53 inode->i_op = &proc_self_inode_operations; 54 d_add(self, inode); 55 ret = 0; 56 } else { 57 dput(self); 58 } 59 } 60 inode_unlock(root_inode); 61 62 if (ret) 63 pr_err("proc_fill_super: can't allocate /proc/self\n"); 64 else 65 ns->proc_self = self; 66 67 return ret; 68 } 69 70 void __init proc_self_init(void) 71 { 72 proc_alloc_inum(&self_inum); 73 } 74