video: fbdev: vt8623fb: Error out if 'pixclock' equals zero

The userspace program could pass any values to the driver through
ioctl() interface. If the driver doesn't check the value of 'pixclock',
it may cause divide error.

Fix this by checking whether 'pixclock' is zero in the function
vt8623fb_check_var().

The following log reveals it:
 divide error: 0000 [#1] PREEMPT SMP KASAN PTI
 RIP: 0010:vt8623fb_set_par+0xecd/0x2210
 Call Trace:
  <TASK>
  fb_set_var+0x604/0xeb0
  do_fb_ioctl+0x234/0x670
  fb_ioctl+0xdd/0x130
  do_syscall_64+0x3b/0x90

Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/drivers/video/fbdev/vt8623fb.c b/drivers/video/fbdev/vt8623fb.c
index 7a959e5ba90b83b9a3cf7a3f844274f094019b6b..a92a8c670cf0f28ffda9c391578bd5d51ba69ee0 100644 (file)
--- a/drivers/video/fbdev/vt8623fb.c
+++ b/drivers/video/fbdev/vt8623fb.c
@@ -321,6 +321,9 @@ static int vt8623fb_check_var(struct fb_var_screeninfo *var, struct fb_info *inf
 {
        int rv, mem, step;
 
+       if (!var->pixclock)
+               return -EINVAL;
+
        /* Find appropriate format */
        rv = svga_match_format (vt8623fb_formats, var, NULL);
        if (rv < 0)