| 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 | 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 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 | else |
| 65 | fs_info->proc_self = self; |
| 66 | |
| 67 | return ret; |
| 68 | } |
| 69 | |
| 70 | void __init proc_self_init(void) |
| 71 | { |
| 72 | proc_alloc_inum(&self_inum); |
| 73 | } |