VT: Bump font size limitation to 64x128 pixels

This moves 32x32 font size limitation checking down to drivers, so that
fbcon can allow large fonts.

We still keep a limitation to 64x128 pixels so as to have a simple bounded
allocation for con_font_get and in the userland kbd tool. That glyph size
will however be enough to have 128x36 characters on a "16/9 8K display".

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/20230119151935.112415738@ens-lyon.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 8da7ab3..57a5c23 100644 (file)
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -4523,17 +4523,20 @@ void reset_palette(struct vc_data *vc)
 /*
  *  Font switching
  *
- *  Currently we only support fonts up to 32 pixels wide, at a maximum height
- *  of 32 pixels. Userspace fontdata is stored with 32 bytes (shorts/ints, 
- *  depending on width) reserved for each character which is kinda wasty, but 
- *  this is done in order to maintain compatibility with the EGA/VGA fonts. It 
- *  is up to the actual low-level console-driver convert data into its favorite
- *  format (maybe we should add a `fontoffset' field to the `display'
- *  structure so we won't have to convert the fontdata all the time.
+ *  Currently we only support fonts up to 128 pixels wide, at a maximum height
+ *  of 128 pixels. Userspace fontdata may have to be stored with 32 bytes
+ *  (shorts/ints, depending on width) reserved for each character which is
+ *  kinda wasty, but this is done in order to maintain compatibility with the
+ *  EGA/VGA fonts. It is up to the actual low-level console-driver convert data
+ *  into its favorite format (maybe we should add a `fontoffset' field to the
+ *  `display' structure so we won't have to convert the fontdata all the time.
  *  /Jes
  */
 
-#define max_font_size 65536
+#define max_font_width 64
+#define max_font_height        128
+#define max_font_glyphs        512
+#define max_font_size  (max_font_glyphs*max_font_width*max_font_height)
 
 static int con_font_get(struct vc_data *vc, struct console_font_op *op)
 {
@@ -4543,7 +4546,7 @@ static int con_font_get(struct vc_data *vc, struct console_font_op *op)
        unsigned int vpitch = op->op == KD_FONT_OP_GET_TALL ? op->height : 32;
 
        if (op->data) {
-               font.data = kmalloc(max_font_size, GFP_KERNEL);
+               font.data = kvmalloc(max_font_size, GFP_KERNEL);
                if (!font.data)
                        return -ENOMEM;
        } else
@@ -4578,7 +4581,7 @@ static int con_font_get(struct vc_data *vc, struct console_font_op *op)
                rc = -EFAULT;
 
 out:
-       kfree(font.data);
+       kvfree(font.data);
        return rc;
 }
 
@@ -4593,9 +4596,10 @@ static int con_font_set(struct vc_data *vc, struct console_font_op *op)
                return -EINVAL;
        if (!op->data)
                return -EINVAL;
-       if (op->charcount > 512)
+       if (op->charcount > max_font_glyphs)
                return -EINVAL;
-       if (op->width <= 0 || op->width > 32 || !op->height || op->height > 32)
+       if (op->width <= 0 || op->width > max_font_width || !op->height ||
+           op->height > max_font_height)
                return -EINVAL;
        if (vpitch < op->height)
                return -EINVAL;

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index 03c2cce..e25ba52 100644 (file)
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -1037,7 +1037,7 @@ static int vgacon_font_set(struct vc_data *c, struct console_font *font,
        if (vga_video_type < VIDEO_TYPE_EGAM)
                return -EINVAL;
 
-       if (font->width != VGA_FONTWIDTH || vpitch != 32 ||
+       if (font->width != VGA_FONTWIDTH || font->height > 32 || vpitch != 32 ||
            (charcount != 256 && charcount != 512))
                return -EINVAL;
 

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 7cd7346..5fb670b 100644 (file)
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -2279,6 +2279,8 @@ static int fbcon_get_font(struct vc_data *vc, struct console_font *font, unsigne
 
        font->width = vc->vc_font.width;
        font->height = vc->vc_font.height;
+       if (font->height > vpitch)
+               return -ENOSPC;
        font->charcount = vc->vc_hi_font_mask ? 512 : 256;
        if (!font->data)
                return 0;