On Mon, Apr 4, 2022 at 3:50 PM Zheyu Ma <zheyuma97@xxxxxxxxx> wrote:
> 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:
>
> [ 511.141561] divide error: 0000 [#1] PREEMPT SMP KASAN PTI
> [ 511.141607] RIP: 0010:s3fb_check_var+0x3f3/0x530
> [ 511.141693] Call Trace:
> [ 511.141695] <TASK>
> [ 511.141716] fb_set_var+0x367/0xeb0
> [ 511.141815] do_fb_ioctl+0x234/0x670
> [ 511.141876] fb_ioctl+0xdd/0x130
> [ 511.141888] do_syscall_64+0x3b/0x90
>
> Signed-off-by: Zheyu Ma <zheyuma97@xxxxxxxxx>
> ---
> drivers/video/fbdev/s3fb.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/video/fbdev/s3fb.c b/drivers/video/fbdev/s3fb.c
> index 5c74253e7b2c..b93c8eb02336 100644
> --- a/drivers/video/fbdev/s3fb.c
> +++ b/drivers/video/fbdev/s3fb.c
> @@ -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;
> +
When passed an invalid value, .check_var() is supposed to
round up the invalid value to a valid value, if possible.
> /* Find appropriate format */
> rv = svga_match_format (s3fb_formats, var, NULL);
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
