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video: fbdev: s3fb: Error out if 'pixclock' equals zero

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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 s3fb_check_var().

The following log reveals it:
 divide error: 0000 [#1] PREEMPT SMP KASAN PTI
 RIP: 0010:s3fb_check_var+0x3f3/0x530
 Call Trace:
  <TASK>
  fb_set_var+0x367/0xeb0
  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>
This commit is contained in:
Zheyu Ma 2022-04-04 16:47:23 +08:00 committed by Helge Deller
parent e1e9651564
commit 7015bb57c3
1 changed files with 3 additions and 0 deletions
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3
drivers/video/fbdev/s3fb.c
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@ -549,6 +549,9 @@ static int s3fb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
int rv, mem, step;
u16 m, n, r;
if (!var->pixclock)
return -EINVAL;
/* Find appropriate format */
rv = svga_match_format (s3fb_formats, var, NULL);