[PATCH] vt: Don't exceed max_font_size on copy in con_font_get()

[Roel Kluin <roel.kluin@gmail.com>]

font.data is kmallocd with max_font_size (defined 65536). Below occurs a
copy_to_user with `c' as a size argument. Ensure we don't copy too much.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
---
 drivers/char/vt.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

If it is possible for c to be greater than 65536 then I think we may need this.
Correct?

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index 0c80c68..045af83 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -3861,6 +3861,10 @@ static int con_font_get(struct vc_data *vc, struct console_font_op *op)
 		goto out;
 
 	c = (font.width+7)/8 * 32 * font.charcount;
+	if (c > max_font_size) {
+		rc = -EINVAL;
+		goto out;
+	}
 
 	if (op->data && font.charcount > op->charcount)
 		rc = -ENOSPC;