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/thread_self: 10 */ 11 static const char *proc_thread_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 pid_t pid = task_pid_nr_ns(current, ns); 18 char *name; 19 20 if (!pid) 21 return ERR_PTR(-ENOENT); 22 name = kmalloc(10 + 6 + 10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC); 23 if (unlikely(!name)) 24 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD); 25 sprintf(name, "%u/task/%u", tgid, pid); 26 set_delayed_call(done, kfree_link, name); 27 return name; 28 } 29 30 static const struct inode_operations proc_thread_self_inode_operations = { 31 .get_link = proc_thread_self_get_link, 32 }; 33 34 static unsigned thread_self_inum __ro_after_init; 35 36 int proc_setup_thread_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 *thread_self; 41 42 inode_lock(root_inode); 43 thread_self = d_alloc_name(s->s_root, "thread-self"); 44 if (thread_self) { 45 struct inode *inode = new_inode_pseudo(s); 46 if (inode) { 47 inode->i_ino = thread_self_inum; 48 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 49 inode->i_mode = S_IFLNK | S_IRWXUGO; 50 inode->i_uid = GLOBAL_ROOT_UID; 51 inode->i_gid = GLOBAL_ROOT_GID; 52 inode->i_op = &proc_thread_self_inode_operations; 53 d_add(thread_self, inode); 54 } else { 55 dput(thread_self); 56 thread_self = ERR_PTR(-ENOMEM); 57 } 58 } else { 59 thread_self = ERR_PTR(-ENOMEM); 60 } 61 inode_unlock(root_inode); 62 if (IS_ERR(thread_self)) { 63 pr_err("proc_fill_super: can't allocate /proc/thread_self\n"); 64 return PTR_ERR(thread_self); 65 } 66 ns->proc_thread_self = thread_self; 67 return 0; 68 } 69 70 void __init proc_thread_self_init(void) 71 { 72 proc_alloc_inum(&thread_self_inum); 73 } 74