1 #include <linux/sched.h> 2 #include <linux/namei.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 vfs_readlink(dentry,buffer,buflen,tmp); 19 } 20 21 static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd) 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 = ERR_PTR(-ENOENT); 26 if (tgid) { 27 /* 11 for max length of signed int in decimal + NULL term */ 28 name = kmalloc(12, GFP_KERNEL); 29 if (!name) 30 name = ERR_PTR(-ENOMEM); 31 else 32 sprintf(name, "%d", tgid); 33 } 34 nd_set_link(nd, name); 35 return NULL; 36 } 37 38 static void proc_self_put_link(struct dentry *dentry, struct nameidata *nd, 39 void *cookie) 40 { 41 char *s = nd_get_link(nd); 42 if (!IS_ERR(s)) 43 kfree(s); 44 } 45 46 static const struct inode_operations proc_self_inode_operations = { 47 .readlink = proc_self_readlink, 48 .follow_link = proc_self_follow_link, 49 .put_link = proc_self_put_link, 50 }; 51 52 static unsigned self_inum; 53 54 int proc_setup_self(struct super_block *s) 55 { 56 struct inode *root_inode = s->s_root->d_inode; 57 struct pid_namespace *ns = s->s_fs_info; 58 struct dentry *self; 59 60 mutex_lock(&root_inode->i_mutex); 61 self = d_alloc_name(s->s_root, "self"); 62 if (self) { 63 struct inode *inode = new_inode_pseudo(s); 64 if (inode) { 65 inode->i_ino = self_inum; 66 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; 67 inode->i_mode = S_IFLNK | S_IRWXUGO; 68 inode->i_uid = GLOBAL_ROOT_UID; 69 inode->i_gid = GLOBAL_ROOT_GID; 70 inode->i_op = &proc_self_inode_operations; 71 d_add(self, inode); 72 } else { 73 dput(self); 74 self = ERR_PTR(-ENOMEM); 75 } 76 } else { 77 self = ERR_PTR(-ENOMEM); 78 } 79 mutex_unlock(&root_inode->i_mutex); 80 if (IS_ERR(self)) { 81 pr_err("proc_fill_super: can't allocate /proc/self\n"); 82 return PTR_ERR(self); 83 } 84 ns->proc_self = self; 85 return 0; 86 } 87 88 void __init proc_self_init(void) 89 { 90 proc_alloc_inum(&self_inum); 91 } 92