[PATCH 5.10 1/1] video: fbdev: i740fb: Error out if 'pixclock' equals zero

[PATCH 5.10 1/1] video: fbdev: i740fb: Error out if 'pixclock' equals zero

[Stefan Ghinea]

From: Zheyu Ma <zheyuma97@gmail.com>

commit 15cf0b82271b1823fb02ab8c377badba614d95d5 upstream

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
i740fb_check_var().

The following log reveals it:

divide error: 0000 [#1] PREEMPT SMP KASAN PTI
RIP: 0010:i740fb_decode_var drivers/video/fbdev/i740fb.c:444 [inline]
RIP: 0010:i740fb_set_par+0x272f/0x3bb0 drivers/video/fbdev/i740fb.c:739
Call Trace:
    fb_set_var+0x604/0xeb0 drivers/video/fbdev/core/fbmem.c:1036
    do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1112
    fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1191
    vfs_ioctl fs/ioctl.c:51 [inline]
    __do_sys_ioctl fs/ioctl.c:874 [inline]

Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Stefan Ghinea <stefan.ghinea@windriver.com>
---
 drivers/video/fbdev/i740fb.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/video/fbdev/i740fb.c b/drivers/video/fbdev/i740fb.c
index ad5ced4ef972..8fb4e01e1943 100644
--- a/drivers/video/fbdev/i740fb.c
+++ b/drivers/video/fbdev/i740fb.c
@@ -662,6 +662,9 @@ static int i740fb_decode_var(const struct fb_var_screeninfo *var,
 
 static int i740fb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
 {
+	if (!var->pixclock)
+		return -EINVAL;
+
 	switch (var->bits_per_pixel) {
 	case 8:
 		var->red.offset	= var->green.offset = var->blue.offset = 0;
-- 
2.37.3

Re: [PATCH 5.10 1/1] video: fbdev: i740fb: Error out if 'pixclock' equals zero

[Greg KH]

On Tue, Sep 20, 2022 at 12:03:02AM +0300, Stefan Ghinea wrote:
> From: Zheyu Ma <zheyuma97@gmail.com>
> 
> commit 15cf0b82271b1823fb02ab8c377badba614d95d5 upstream
> 
> 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
> i740fb_check_var().
> 
> The following log reveals it:
> 
> divide error: 0000 [#1] PREEMPT SMP KASAN PTI
> RIP: 0010:i740fb_decode_var drivers/video/fbdev/i740fb.c:444 [inline]
> RIP: 0010:i740fb_set_par+0x272f/0x3bb0 drivers/video/fbdev/i740fb.c:739
> Call Trace:
>     fb_set_var+0x604/0xeb0 drivers/video/fbdev/core/fbmem.c:1036
>     do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1112
>     fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1191
>     vfs_ioctl fs/ioctl.c:51 [inline]
>     __do_sys_ioctl fs/ioctl.c:874 [inline]
> 
> Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
> Signed-off-by: Helge Deller <deller@gmx.de>
> Signed-off-by: Stefan Ghinea <stefan.ghinea@windriver.com>
> ---
>  drivers/video/fbdev/i740fb.c | 3 +++
>  1 file changed, 3 insertions(+)

Both backports now queued up, thanks.

greg k-h