eCryptfs: do not try to open device files on mknod

When creating device nodes, eCryptfs needs to delay actually opening the lower
persistent file until an application tries to open.  Device handles may not be
backed by anything when they first come into existence.

[Valdis.Kletnieks@vt.edu: build fix]
Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
Cc: <Valdis.Kletnieks@vt.edu}
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ecryptfs/ecryptfs_kernel.h

@@ -235,6 +235,7 @@ struct ecryptfs_crypt_stat {
 #define ECRYPTFS_METADATA_IN_XATTR  0x00000100
 #define ECRYPTFS_VIEW_AS_ENCRYPTED  0x00000200
 #define ECRYPTFS_KEY_SET            0x00000400
+#define ECRYPTFS_DELAY_PERSISTENT   0x00000800
 	u32 flags;
 	unsigned int file_version;
 	size_t iv_bytes;
@@ -574,9 +575,11 @@ struct ecryptfs_open_req {
 	struct list_head kthread_ctl_list;
 };
 
+#define ECRYPTFS_INTERPOSE_FLAG_D_ADD                 0x00000001
+#define ECRYPTFS_INTERPOSE_FLAG_DELAY_PERSISTENT_FILE 0x00000002
 int ecryptfs_interpose(struct dentry *hidden_dentry,
 		       struct dentry *this_dentry, struct super_block *sb,
-		       int flag);
+		       u32 flags);
 int ecryptfs_fill_zeros(struct file *file, loff_t new_length);
 int ecryptfs_decode_filename(struct ecryptfs_crypt_stat *crypt_stat,
 			     const char *name, int length,
@@ -709,5 +712,6 @@ void ecryptfs_destroy_kthread(void);
 int ecryptfs_privileged_open(struct file **lower_file,
 			     struct dentry *lower_dentry,
 			     struct vfsmount *lower_mnt);
+int ecryptfs_init_persistent_file(struct dentry *ecryptfs_dentry);
 
 #endif /* #ifndef ECRYPTFS_KERNEL_H */

fs/ecryptfs/file.c

@@ -199,6 +199,20 @@ static int ecryptfs_open(struct inode *inode, struct file *file)
 		       "file must hence be opened RO\n", __func__);
 		goto out;
 	}
+	if (!ecryptfs_inode_to_private(inode)->lower_file) {
+		BUG_ON(!(crypt_stat->flags & ECRYPTFS_DELAY_PERSISTENT));
+		mutex_lock(&crypt_stat->cs_mutex);
+		crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
+		mutex_unlock(&crypt_stat->cs_mutex);
+		rc = ecryptfs_init_persistent_file(ecryptfs_dentry);
+		if (rc) {
+			printk(KERN_ERR "%s: Error attempting to initialize "
+			       "the persistent file for the dentry with name "
+			       "[%s]; rc = [%d]\n", __func__,
+			       ecryptfs_dentry->d_name.name, rc);
+			goto out;
+		}
+	}
 	ecryptfs_set_file_lower(
 		file, ecryptfs_inode_to_private(inode)->lower_file);
 	if (S_ISDIR(ecryptfs_dentry->d_inode->i_mode)) {

fs/ecryptfs/inode.c

@@ -308,7 +308,8 @@ static struct dentry *ecryptfs_lookup(struct inode *dir, struct dentry *dentry,
 		d_add(dentry, NULL);
 		goto out;
 	}
-	rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb, 1);
+	rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb,
+				ECRYPTFS_INTERPOSE_FLAG_D_ADD);
 	if (rc) {
 		ecryptfs_printk(KERN_ERR, "Error interposing\n");
 		goto out_dput;
@@ -537,7 +538,8 @@ ecryptfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 	rc = vfs_mknod(lower_dir_dentry->d_inode, lower_dentry, mode, dev);
 	if (rc || !lower_dentry->d_inode)
 		goto out;
-	rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb, 0);
+	rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb,
+				ECRYPTFS_INTERPOSE_FLAG_DELAY_PERSISTENT_FILE);
 	if (rc)
 		goto out;
 	fsstack_copy_attr_times(dir, lower_dir_dentry->d_inode);

fs/ecryptfs/main.c

@@ -117,7 +117,7 @@ void __ecryptfs_printk(const char *fmt, ...)
  *
  * Returns zero on success; non-zero otherwise
  */
-static int ecryptfs_init_persistent_file(struct dentry *ecryptfs_dentry)
+int ecryptfs_init_persistent_file(struct dentry *ecryptfs_dentry)
 {
 	struct ecryptfs_inode_info *inode_info =
 		ecryptfs_inode_to_private(ecryptfs_dentry->d_inode);
@@ -149,14 +149,14 @@ static int ecryptfs_init_persistent_file(struct dentry *ecryptfs_dentry)
  * @lower_dentry: Existing dentry in the lower filesystem
  * @dentry: ecryptfs' dentry
  * @sb: ecryptfs's super_block
- * @flag: If set to true, then d_add is called, else d_instantiate is called
+ * @flags: flags to govern behavior of interpose procedure
  *
  * Interposes upper and lower dentries.
  *
  * Returns zero on success; non-zero otherwise
  */
 int ecryptfs_interpose(struct dentry *lower_dentry, struct dentry *dentry,
-		       struct super_block *sb, int flag)
+		       struct super_block *sb, u32 flags)
 {
 	struct inode *lower_inode;
 	struct inode *inode;
@@ -193,20 +193,29 @@ int ecryptfs_interpose(struct dentry *lower_dentry, struct dentry *dentry,
 		init_special_inode(inode, lower_inode->i_mode,
 				   lower_inode->i_rdev);
 	dentry->d_op = &ecryptfs_dops;
-	if (flag)
+	if (flags & ECRYPTFS_INTERPOSE_FLAG_D_ADD)
 		d_add(dentry, inode);
 	else
 		d_instantiate(dentry, inode);
 	fsstack_copy_attr_all(inode, lower_inode, NULL);
 	/* This size will be overwritten for real files w/ headers and
 	 * other metadata */
 	fsstack_copy_inode_size(inode, lower_inode);
-	rc = ecryptfs_init_persistent_file(dentry);
-	if (rc) {
-		printk(KERN_ERR "%s: Error attempting to initialize the "
-		       "persistent file for the dentry with name [%s]; "
-		       "rc = [%d]\n", __func__, dentry->d_name.name, rc);
-		goto out;
+	if (!(flags & ECRYPTFS_INTERPOSE_FLAG_DELAY_PERSISTENT_FILE)) {
+		rc = ecryptfs_init_persistent_file(dentry);
+		if (rc) {
+			printk(KERN_ERR "%s: Error attempting to initialize "
+			       "the persistent file for the dentry with name "
+			       "[%s]; rc = [%d]\n", __func__,
+			       dentry->d_name.name, rc);
+			goto out;
+		}
+	} else {
+		struct ecryptfs_inode_info *inode_info =
+			ecryptfs_inode_to_private(dentry->d_inode);
+
+		inode_info->lower_file = NULL;
+		inode_info->crypt_stat.flags |= ECRYPTFS_DELAY_PERSISTENT;
 	}
 out:
 	return rc;