[PATCH 1/7] video: fbdev: i740fb: Error out if 'pixclock' equals zero

From: Zheyu Ma
Date: Mon Apr 04 2022 - 04:48:16 EST

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

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@xxxxxxxxx>
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 52cce0db8bd3..b595437a5752 100644
--- a/drivers/video/fbdev/i740fb.c
+++ b/drivers/video/fbdev/i740fb.c
@@ -657,6 +657,9 @@ 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;