[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, 42 deletions

diff --git a/arch/s390/hypfs/hypfs_vm.c b/arch/s390/hypfs/hypfs_vm.c
index 26cf177f6a3a..e54796002f61 100644
--- a/arch/s390/hypfs/hypfs_vm.c
+++ b/arch/s390/hypfs/hypfs_vm.c
@@ -20,8 +20,6 @@ static char local_guest[] = "        ";
 static char all_guests[] = "*       ";
 static char *guest_query;
 
-static struct dentry *dbfs_d2fc_file;
-
 struct diag2fc_data {
 	__u32 version;
 	__u32 flags;
@@ -104,7 +102,7 @@ static void *diag2fc_store(char *query, unsigned int *count, int offset)
 	return data;
 }
 
-static void diag2fc_free(void *data)
+static void diag2fc_free(const void *data)
 {
 	vfree(data);
 }
@@ -239,43 +237,29 @@ struct dbfs_d2fc {
 	char			buf[];	/* d2fc buffer */
 } __attribute__ ((packed));
 
-static int dbfs_d2fc_open(struct inode *inode, struct file *file)
+static int dbfs_diag2fc_create(void **data, void **data_free_ptr, size_t *size)
 {
-	struct dbfs_d2fc *data;
+	struct dbfs_d2fc *d2fc;
 	unsigned int count;
 
-	data = diag2fc_store(guest_query, &count, sizeof(data->hdr));
-	if (IS_ERR(data))
-		return PTR_ERR(data);
-	get_clock_ext(data->hdr.tod_ext);
-	data->hdr.len = count * sizeof(struct diag2fc_data);
-	data->hdr.version = DBFS_D2FC_HDR_VERSION;
-	data->hdr.count = count;
-	memset(&data->hdr.reserved, 0, sizeof(data->hdr.reserved));
-	file->private_data = data;
-	return nonseekable_open(inode, file);
-}
-
-static int dbfs_d2fc_release(struct inode *inode, struct file *file)
-{
-	diag2fc_free(file->private_data);
+	d2fc = diag2fc_store(guest_query, &count, sizeof(d2fc->hdr));
+	if (IS_ERR(d2fc))
+		return PTR_ERR(d2fc);
+	get_clock_ext(d2fc->hdr.tod_ext);
+	d2fc->hdr.len = count * sizeof(struct diag2fc_data);
+	d2fc->hdr.version = DBFS_D2FC_HDR_VERSION;
+	d2fc->hdr.count = count;
+	memset(&d2fc->hdr.reserved, 0, sizeof(d2fc->hdr.reserved));
+	*data = d2fc;
+	*data_free_ptr = d2fc;
+	*size = d2fc->hdr.len + sizeof(struct dbfs_d2fc_hdr);
 	return 0;
 }
 
-static ssize_t dbfs_d2fc_read(struct file *file, char __user *buf,
-				    size_t size, loff_t *ppos)
-{
-	struct dbfs_d2fc *data = file->private_data;
-
-	return simple_read_from_buffer(buf, size, ppos, data, data->hdr.len +
-				       sizeof(struct dbfs_d2fc_hdr));
-}
-
-static const struct file_operations dbfs_d2fc_ops = {
-	.open		= dbfs_d2fc_open,
-	.read		= dbfs_d2fc_read,
-	.release	= dbfs_d2fc_release,
-	.llseek		= no_llseek,
+static struct hypfs_dbfs_file dbfs_file_2fc = {
+	.name		= "diag_2fc",
+	.data_create	= dbfs_diag2fc_create,
+	.data_free	= diag2fc_free,
 };
 
 int hypfs_vm_init(void)
@@ -288,18 +272,12 @@ int hypfs_vm_init(void)
 		guest_query = local_guest;
 	else
 		return -EACCES;
-
-	dbfs_d2fc_file = debugfs_create_file("diag_2fc", 0400, hypfs_dbfs_dir,
-					     NULL, &dbfs_d2fc_ops);
-	if (IS_ERR(dbfs_d2fc_file))
-		return PTR_ERR(dbfs_d2fc_file);
-
-	return 0;
+	return hypfs_dbfs_create_file(&dbfs_file_2fc);
 }
 
 void hypfs_vm_exit(void)
 {
 	if (!MACHINE_IS_VM)
 		return;
-	debugfs_remove(dbfs_d2fc_file);
+	hypfs_dbfs_remove_file(&dbfs_file_2fc);
 }