[S390] hypfs: Move buffer allocation from open to read

Currently the buffer for diagnose data is allocated in the open function
of the debugfs file and is released in the close function. This has the
drawback that a user (root) can pin that memory by not closing the file.
This patch moves the buffer allocation to the read function. The buffer is
automatically released after the buffer is copied to userspace.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 7 insertions, 11 deletions

diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
index 47cc446dab8f..6fe874fc5f8e 100644
--- a/arch/s390/hypfs/inode.c
+++ b/arch/s390/hypfs/inode.c
@@ -46,8 +46,6 @@ static const struct super_operations hypfs_s_ops;
 /* start of list of all dentries, which have to be deleted on update */
 static struct dentry *hypfs_last_dentry;
 
-struct dentry *hypfs_dbfs_dir;
-
 static void hypfs_update_update(struct super_block *sb)
 {
 	struct hypfs_sb_info *sb_info = sb->s_fs_info;
@@ -471,13 +469,12 @@ static int __init hypfs_init(void)
 {
 	int rc;
 
-	hypfs_dbfs_dir = debugfs_create_dir("s390_hypfs", NULL);
-	if (IS_ERR(hypfs_dbfs_dir))
-		return PTR_ERR(hypfs_dbfs_dir);
-
+	rc = hypfs_dbfs_init();
+	if (rc)
+		return rc;
 	if (hypfs_diag_init()) {
 		rc = -ENODATA;
-		goto fail_debugfs_remove;
+		goto fail_dbfs_exit;
 	}
 	if (hypfs_vm_init()) {
 		rc = -ENODATA;
@@ -499,9 +496,8 @@ fail_hypfs_vm_exit:
 	hypfs_vm_exit();
 fail_hypfs_diag_exit:
 	hypfs_diag_exit();
-fail_debugfs_remove:
-	debugfs_remove(hypfs_dbfs_dir);
-
+fail_dbfs_exit:
+	hypfs_dbfs_exit();
 	pr_err("Initialization of hypfs failed with rc=%i\n", rc);
 	return rc;
 }
@@ -510,7 +506,7 @@ static void __exit hypfs_exit(void)
 {
 	hypfs_diag_exit();
 	hypfs_vm_exit();
-	debugfs_remove(hypfs_dbfs_dir);
+	hypfs_dbfs_exit();
 	unregister_filesystem(&hypfs_type);
 	kobject_put(s390_kobj);
 }