[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, 20 insertions, 62 deletions

diff --git a/arch/s390/hypfs/hypfs_diag.c b/arch/s390/hypfs/hypfs_diag.c
index cd4a81b..6023c6d 100644
--- a/arch/s390/hypfs/hypfs_diag.c
+++ b/arch/s390/hypfs/hypfs_diag.c
@@ -555,81 +555,38 @@ struct dbfs_d204 {
 	char			buf[];	/* d204 buffer */
 } __attribute__ ((packed));
 
-struct dbfs_d204_private {
-	struct dbfs_d204	*d204;	/* Aligned d204 data with header */
-	void			*base;	/* Base pointer (needed for vfree) */
-};
-
-static int dbfs_d204_open(struct inode *inode, struct file *file)
+static int dbfs_d204_create(void **data, void **data_free_ptr, size_t *size)
 {
-	struct dbfs_d204_private *data;
 	struct dbfs_d204 *d204;
 	int rc, buf_size;
+	void *base;
 
-	data = kzalloc(sizeof(*data), GFP_KERNEL);
-	if (!data)
-		return -ENOMEM;
 	buf_size = PAGE_SIZE * (diag204_buf_pages + 1) + sizeof(d204->hdr);
-	data->base = vmalloc(buf_size);
-	if (!data->base) {
-		rc = -ENOMEM;
-		goto fail_kfree_data;
+	base = vmalloc(buf_size);
+	if (!base)
+		return -ENOMEM;
+	memset(base, 0, buf_size);
+	d204 = page_align_ptr(base + sizeof(d204->hdr)) - sizeof(d204->hdr);
+	rc = diag204_do_store(d204->buf, diag204_buf_pages);
+	if (rc) {
+		vfree(base);
+		return rc;
 	}
-	memset(data->base, 0, buf_size);
-	d204 = page_align_ptr(data->base + sizeof(d204->hdr))
-		- sizeof(d204->hdr);
-	rc = diag204_do_store(&d204->buf, diag204_buf_pages);
-	if (rc)
-		goto fail_vfree_base;
 	d204->hdr.version = DBFS_D204_HDR_VERSION;
 	d204->hdr.len = PAGE_SIZE * diag204_buf_pages;
 	d204->hdr.sc = diag204_store_sc;
-	data->d204 = d204;
-	file->private_data = data;
-	return nonseekable_open(inode, file);
-
-fail_vfree_base:
-	vfree(data->base);
-fail_kfree_data:
-	kfree(data);
-	return rc;
-}
-
-static int dbfs_d204_release(struct inode *inode, struct file *file)
-{
-	struct dbfs_d204_private *data = file->private_data;
-
-	vfree(data->base);
-	kfree(data);
+	*data = d204;
+	*data_free_ptr = base;
+	*size = d204->hdr.len + sizeof(struct dbfs_d204_hdr);
 	return 0;
 }
 
-static ssize_t dbfs_d204_read(struct file *file, char __user *buf,
-			      size_t size, loff_t *ppos)
-{
-	struct dbfs_d204_private *data = file->private_data;
-
-	return simple_read_from_buffer(buf, size, ppos, data->d204,
-				       data->d204->hdr.len +
-				       sizeof(data->d204->hdr));
-}
-
-static const struct file_operations dbfs_d204_ops = {
-	.open		= dbfs_d204_open,
-	.read		= dbfs_d204_read,
-	.release	= dbfs_d204_release,
-	.llseek		= no_llseek,
+static struct hypfs_dbfs_file dbfs_file_d204 = {
+	.name		= "diag_204",
+	.data_create	= dbfs_d204_create,
+	.data_free	= vfree,
 };
 
-static int hypfs_dbfs_init(void)
-{
-	dbfs_d204_file = debugfs_create_file("diag_204", 0400, hypfs_dbfs_dir,
-					     NULL, &dbfs_d204_ops);
-	if (IS_ERR(dbfs_d204_file))
-		return PTR_ERR(dbfs_d204_file);
-	return 0;
-}
-
 __init int hypfs_diag_init(void)
 {
 	int rc;
@@ -639,7 +596,7 @@ __init int hypfs_diag_init(void)
 		return -ENODATA;
 	}
 	if (diag204_info_type == INFO_EXT) {
-		rc = hypfs_dbfs_init();
+		rc = hypfs_dbfs_create_file(&dbfs_file_d204);
 		if (rc)
 			return rc;
 	}
@@ -660,6 +617,7 @@ void hypfs_diag_exit(void)
 	debugfs_remove(dbfs_d204_file);
 	diag224_delete_name_table();
 	diag204_free_buffer();
+	hypfs_dbfs_remove_file(&dbfs_file_d204);
 }
 
 /*