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 vfs_readlink(dentry,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 void proc_self_put_link(struct dentry *dentry, struct nameidata *nd, 40 void *cookie) 41 { 42 char *s = nd_get_link(nd); 43 if (!IS_ERR(s)) 44 kfree(s); 45 } 46 47 static const struct inode_operations proc_self_inode_operations = { 48 .readlink = proc_self_readlink, 49 .follow_link = proc_self_follow_link, 50 .put_link = proc_self_put_link, 51 }; 52 53 static unsigned self_inum; 54 55 int proc_setup_self(struct super_block *s) 56 { 57 struct inode *root_inode = s->s_root->d_inode; 58 struct pid_namespace *ns = s->s_fs_info; 59 struct dentry *self; 60 61 mutex_lock(&root_inode->i_mutex); 62 self = d_alloc_name(s->s_root, "self"); 63 if (self) { 64 struct inode *inode = new_inode_pseudo(s); 65 if (inode) { 66 inode->i_ino = self_inum; 67 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; 68 inode->i_mode = S_IFLNK | S_IRWXUGO; 69 inode->i_uid = GLOBAL_ROOT_UID; 70 inode->i_gid = GLOBAL_ROOT_GID; 71 inode->i_op = &proc_self_inode_operations; 72 d_add(self, inode); 73 } else { 74 dput(self); 75 self = ERR_PTR(-ENOMEM); 76 } 77 } else { 78 self = ERR_PTR(-ENOMEM); 79 } 80 mutex_unlock(&root_inode->i_mutex); 81 if (IS_ERR(self)) { 82 pr_err("proc_fill_super: can't allocate /proc/self\n"); 83 return PTR_ERR(self); 84 } 85 ns->proc_self = self; 86 return 0; 87 } 88 89 void __init proc_self_init(void) 90 { 91 proc_alloc_inum(&self_inum); 92 } 93