fbdev, newport_con: Move FONT_EXTRA_WORDS macros into linux/font.h

stable inclusion
from linux-4.19.151
commit 7b9eaa7241ea2cfa580b854d461be72107a4b35c
CVE: CVE-2020-28915

It's prepare for fixing CVE-2020-28915.

--------------------------------

commit bb0890b4 upstream.

drivers/video/console/newport_con.c is borrowing FONT_EXTRA_WORDS macros
from drivers/video/fbdev/core/fbcon.h. To keep things simple, move all
definitions into <linux/font.h>.

Since newport_con now uses four extra words, initialize the fourth word in
newport_set_font() properly.

Cc: stable@vger.kernel.org
Signed-off-by: NPeilin Ye <yepeilin.cs@gmail.com>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/7fb8bc9b0abc676ada6b7ac0e0bd443499357267.1600953813.git.yepeilin.cs@gmail.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/video/console/newport_con.c

@@ -33,12 +33,6 @@
 
 #define FONT_DATA ((unsigned char *)font_vga_8x16.data)
 
-/* borrowed from fbcon.c */
-#define REFCOUNT(fd)	(((int *)(fd))[-1])
-#define FNTSIZE(fd)	(((int *)(fd))[-2])
-#define FNTCHARCNT(fd)	(((int *)(fd))[-3])
-#define FONT_EXTRA_WORDS 3
-
 static unsigned char *font_data[MAX_NR_CONSOLES];
 
 static struct newport_regs *npregs;
@@ -519,6 +513,7 @@ static int newport_set_font(int unit, struct console_font *op)
 	FNTSIZE(new_data) = size;
 	FNTCHARCNT(new_data) = op->charcount;
 	REFCOUNT(new_data) = 0;	/* usage counter */
+	FNTSUM(new_data) = 0;
 
 	p = new_data;
 	for (i = 0; i < op->charcount; i++) {

drivers/video/fbdev/core/fbcon.h

@@ -152,13 +152,6 @@ static inline int attr_col_ec(int shift, struct vc_data *vc,
 #define attr_bgcol_ec(bgshift, vc, info) attr_col_ec(bgshift, vc, info, 0)
 #define attr_fgcol_ec(fgshift, vc, info) attr_col_ec(fgshift, vc, info, 1)
 
-/* Font */
-#define REFCOUNT(fd)	(((int *)(fd))[-1])
-#define FNTSIZE(fd)	(((int *)(fd))[-2])
-#define FNTCHARCNT(fd)	(((int *)(fd))[-3])
-#define FNTSUM(fd)	(((int *)(fd))[-4])
-#define FONT_EXTRA_WORDS 4
-
     /*
      *  Scroll Method
      */

drivers/video/fbdev/core/fbcon_rotate.c

@@ -14,6 +14,7 @@
 #include <linux/fb.h>
 #include <linux/vt_kern.h>
 #include <linux/console.h>
+#include <linux/font.h>
 #include <asm/types.h>
 #include "fbcon.h"
 #include "fbcon_rotate.h"

drivers/video/fbdev/core/tileblit.c

@@ -13,6 +13,7 @@
 #include <linux/fb.h>
 #include <linux/vt_kern.h>
 #include <linux/console.h>
+#include <linux/font.h>
 #include <asm/types.h>
 #include "fbcon.h"
 

include/linux/font.h

@@ -57,4 +57,12 @@ extern const struct font_desc *get_default_font(int xres, int yres,
 /* Max. length for the name of a predefined font */
 #define MAX_FONT_NAME	32
 
+/* Extra word getters */
+#define REFCOUNT(fd)	(((int *)(fd))[-1])
+#define FNTSIZE(fd)	(((int *)(fd))[-2])
+#define FNTCHARCNT(fd)	(((int *)(fd))[-3])
+#define FNTSUM(fd)	(((int *)(fd))[-4])
+
+#define FONT_EXTRA_WORDS 4
+
 #endif /* _VIDEO_FONT_H */