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video: fbdev: vt8623fb: Check the size of screen before memset_io()
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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: 558b7bd ("vt8623fb: new framebuffer driver for VIA VT8623")
Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>
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Zheyu Ma authored and Helge Deller committed Aug 5, 2022
1 parent 40bf722 commit ec0754c
Showing 1 changed file with 2 additions and 0 deletions.
2 changes: 2 additions & 0 deletions drivers/video/fbdev/vt8623fb.c
Original file line number Diff line number Diff line change
@@ -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 */

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