1 #include <linux/sched.h> 2 #include <linux/namei.h> 3 #include <linux/slab.h> 4 #include <linux/pid_namespace.h> 5 #include "internal.h" 6 7 /* 8 * /proc/self: 9 */ 10 static int proc_self_readlink(struct dentry *dentry, char __user *buffer, 11 int buflen) 12 { 13 struct pid_namespace *ns = dentry->d_sb->s_fs_info; 14 pid_t tgid = task_tgid_nr_ns(current, ns); 15 char tmp[PROC_NUMBUF]; 16 if (!tgid) 17 return -ENOENT; 18 sprintf(tmp, "%d", tgid); 19 return readlink_copy(buffer, buflen, tmp); 20 } 21 22 static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd) 23 { 24 struct pid_namespace *ns = dentry->d_sb->s_fs_info; 25 pid_t tgid = task_tgid_nr_ns(current, ns); 26 char *name = ERR_PTR(-ENOENT); 27 if (tgid) { 28 /* 11 for max length of signed int in decimal + NULL term */ 29 name = kmalloc(12, GFP_KERNEL); 30 if (!name) 31 name = ERR_PTR(-ENOMEM); 32 else 33 sprintf(name, "%d", tgid); 34 } 35 nd_set_link(nd, name); 36 return NULL; 37 } 38 39 static const struct inode_operations proc_self_inode_operations = { 40 .readlink = proc_self_readlink, 41 .follow_link = proc_self_follow_link, 42 .put_link = kfree_put_link, 43 }; 44 45 static unsigned self_inum; 46 47 int proc_setup_self(struct super_block *s) 48 { 49 struct inode *root_inode = d_inode(s->s_root); 50 struct pid_namespace *ns = s->s_fs_info; 51 struct dentry *self; 52 53 mutex_lock(&root_inode->i_mutex); 54 self = d_alloc_name(s->s_root, "self"); 55 if (self) { 56 struct inode *inode = new_inode_pseudo(s); 57 if (inode) { 58 inode->i_ino = self_inum; 59 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; 60 inode->i_mode = S_IFLNK | S_IRWXUGO; 61 inode->i_uid = GLOBAL_ROOT_UID; 62 inode->i_gid = GLOBAL_ROOT_GID; 63 inode->i_op = &proc_self_inode_operations; 64 d_add(self, inode); 65 } else { 66 dput(self); 67 self = ERR_PTR(-ENOMEM); 68 } 69 } else { 70 self = ERR_PTR(-ENOMEM); 71 } 72 mutex_unlock(&root_inode->i_mutex); 73 if (IS_ERR(self)) { 74 pr_err("proc_fill_super: can't allocate /proc/self\n"); 75 return PTR_ERR(self); 76 } 77 ns->proc_self = self; 78 return 0; 79 } 80 81 void __init proc_self_init(void) 82 { 83 proc_alloc_inum(&self_inum); 84 } 85