[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, 31 insertions, 2 deletions

diff --git a/arch/s390/hypfs/hypfs.h b/arch/s390/hypfs/hypfs.h
index fa487d4cc08b..80c1526f2af3 100644
--- a/arch/s390/hypfs/hypfs.h
+++ b/arch/s390/hypfs/hypfs.h
@@ -12,6 +12,8 @@
 #include <linux/fs.h>
 #include <linux/types.h>
 #include <linux/debugfs.h>
+#include <linux/workqueue.h>
+#include <linux/kref.h>
 
 #define REG_FILE_MODE    0440
 #define UPDATE_FILE_MODE 0220
@@ -38,6 +40,33 @@ extern int hypfs_vm_init(void);
 extern void hypfs_vm_exit(void);
 extern int hypfs_vm_create_files(struct super_block *sb, struct dentry *root);
 
-/* Directory for debugfs files */
-extern struct dentry *hypfs_dbfs_dir;
+/* debugfs interface */
+struct hypfs_dbfs_file;
+
+struct hypfs_dbfs_data {
+        void                    *buf;
+        void                    *buf_free_ptr;
+        size_t                  size;
+        struct hypfs_dbfs_file  *dbfs_file;;
+        struct kref             kref;
+};
+
+struct hypfs_dbfs_file {
+        const char      *name;
+        int             (*data_create)(void **data, void **data_free_ptr,
+                                       size_t *size);
+        void            (*data_free)(const void *buf_free_ptr);
+
+        /* Private data for hypfs_dbfs.c */
+        struct hypfs_dbfs_data  *data;
+        struct delayed_work     data_free_work;
+        struct mutex            lock;
+        struct dentry           *dentry;
+};
+
+extern int hypfs_dbfs_init(void);
+extern void hypfs_dbfs_exit(void);
+extern int hypfs_dbfs_create_file(struct hypfs_dbfs_file *df);
+extern void hypfs_dbfs_remove_file(struct hypfs_dbfs_file *df);
+
 #endif /* _HYPFS_H_ */