From 96b550971c65d54d64728d8ba973487878a06454 Mon Sep 17 00:00:00 2001
From: Zheyu Ma <zheyuma97@gmail.com>
Date: Thu, 4 Aug 2022 20:41:24 +0800
Subject: video: fbdev: arkfb: Check the size of screen before memset_io()
Git-commit: 96b550971c65d54d64728d8ba973487878a06454
Patch-mainline: v6.0-rc1
References: bsc#1154048
In the function arkfb_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:
[ 659.399066] BUG: unable to handle page fault for address: ffffc90003000000
[ 659.399077] #PF: supervisor write access in kernel mode
[ 659.399079] #PF: error_code(0x0002) - not-present page
[ 659.399094] RIP: 0010:memset_orig+0x33/0xb0
[ 659.399116] Call Trace:
[ 659.399122] arkfb_set_par+0x143f/0x24c0
[ 659.399130] fb_set_var+0x604/0xeb0
[ 659.399161] do_fb_ioctl+0x234/0x670
[ 659.399189] fb_ioctl+0xdd/0x130
Fix the this by checking the value of 'screen_size' before memset_io().
Fixes: 681e14730c73 ("arkfb: new framebuffer driver for ARK Logic cards")
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/arkfb.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/video/fbdev/arkfb.c b/drivers/video/fbdev/arkfb.c
index ed76ddc7df3d..a2a381631628 100644
--- a/drivers/video/fbdev/arkfb.c
+++ b/drivers/video/fbdev/arkfb.c
@@ -797,6 +797,8 @@ static int arkfb_set_par(struct fb_info *info)
value = ((value * hmul / hdiv) / 8) - 5;
vga_wcrt(par->state.vgabase, 0x42, (value + 1) / 2);
+ if (screen_size > info->screen_size)
+ screen_size = info->screen_size;
memset_io(info->screen_base, 0x00, screen_size);
/* Device and screen back on */
svga_wcrt_mask(par->state.vgabase, 0x17, 0x80, 0x80);
--
2.37.3