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1// SPDX-License-Identifier: GPL-2.02#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 */11static 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 30static const struct inode_operations proc_self_inode_operations = {31 .get_link = proc_self_get_link,32};33 34static unsigned self_inum __ro_after_init;35 36int proc_setup_self(struct super_block *s)37{38 struct inode *root_inode = d_inode(s->s_root);39 struct proc_fs_info *fs_info = proc_sb_info(s);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(s);47 if (inode) {48 inode->i_ino = self_inum;49 simple_inode_init_ts(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 else65 fs_info->proc_self = self;66 67 return ret;68}69 70void __init proc_self_init(void)71{72 proc_alloc_inum(&self_inum);73}74