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

[ Upstream commit e04d54793e947de1cb45c7aba412f68bed9a6f89 ]

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: dbd58d3aadcf ("arkfb: new framebuffer driver for ARK Logic cards")
Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/video/fbdev/arkfb.c b/drivers/video/fbdev/arkfb.c
index d94cc5ad1ef677fbf610e3d2d2f0dad1db284d58..8d092b106470634d358cbde6efe0770d71015406 100644 (file)
--- a/drivers/video/fbdev/arkfb.c
+++ b/drivers/video/fbdev/arkfb.c
@@ -794,6 +794,8 @@ 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);