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