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 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 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 dentry *self; 40 int ret = -ENOMEM; 41 42 inode_lock(root_inode); 43 self = d_alloc_name(s->s_root, "self"); 44 if (self) { 45 struct inode *inode = new_inode(s); 46 if (inode) { 47 inode->i_ino = self_inum; 48 simple_inode_init_ts(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_self_inode_operations; 53 d_make_persistent(self, inode); 54 ret = 0; 55 } 56 dput(self); 57 } 58 inode_unlock(root_inode); 59 60 if (ret) 61 pr_err("proc_fill_super: can't allocate /proc/self\n"); 62 63 return ret; 64 } 65 66 void __init proc_self_init(void) 67 { 68 proc_alloc_inum(&self_inum); 69 } 70