From ec0754c60217248fa77cc9005d66b2b55200ac06 Mon Sep 17 00:00:00 2001

From: Zheyu Ma <zheyuma97@gmail.com>

Date: Thu, 4 Aug 2022 20:41:23 +0800

Subject: video: fbdev: vt8623fb: Check the size of screen before memset_io()

Git-commit: ec0754c60217248fa77cc9005d66b2b55200ac06

Patch-mainline: v6.0-rc1

References: bsc#1154048

In the function vt8623fb_set_par(), the value of 'screen_size' is

calculated by the user input. If the user provides the improper value,

the value of 'screen_size' may larger than 'info->screen_size', which

may cause the following bug:

[  583.339036] BUG: unable to handle page fault for address: ffffc90005000000

[  583.339049] #PF: supervisor write access in kernel mode

[  583.339052] #PF: error_code(0x0002) - not-present page

[  583.339074] RIP: 0010:memset_orig+0x33/0xb0

[  583.339110] Call Trace:

[  583.339118]  vt8623fb_set_par+0x11cd/0x21e0

[  583.339146]  fb_set_var+0x604/0xeb0

[  583.339181]  do_fb_ioctl+0x234/0x670

[  583.339209]  fb_ioctl+0xdd/0x130

Fix the this by checking the value of 'screen_size' before memset_io().

Fixes: 558b7bd86c32 ("vt8623fb: new framebuffer driver for VIA VT8623")

Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>

Signed-off-by: Helge Deller <deller@gmx.de>

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>

---

 drivers/video/fbdev/vt8623fb.c | 2 ++

 1 file changed, 2 insertions(+)

diff --git a/drivers/video/fbdev/vt8623fb.c b/drivers/video/fbdev/vt8623fb.c

index a92a8c670cf0..4274c6efb249 100644

--- a/drivers/video/fbdev/vt8623fb.c

+++ b/drivers/video/fbdev/vt8623fb.c

@@ -507,6 +507,8 @@ static int vt8623fb_set_par(struct fb_info *info)

 			 (info->var.vmode & FB_VMODE_DOUBLE) ? 2 : 1, 1,

 			 1, info->node);

+	if (screen_size > info->screen_size)

+		screen_size = info->screen_size;

 	memset_io(info->screen_base, 0x00, screen_size);

 	/* Device and screen back on */

-- 

2.37.3