linux-kernel - [PATCH] vt: Don't exceed max_font_size on copy in con_font

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Message-ID: <4B0AEF4E.8070005@gmail.com>
Date:	Mon, 23 Nov 2009 21:23:42 +0100
From:	Roel Kluin <roel.kluin@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] vt: Don't exceed max_font_size on copy in con_font_get()

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@...il.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;
--
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