[PATCH AUTOSEL 4.14 7/8] fbdev: fb_pm2fb: Avoid potential divide by zero error

[PATCH AUTOSEL 4.14 7/8] fbdev: fb_pm2fb: Avoid potential divide by zero error

[Sasha Levin]

From: Letu Ren <fantasquex@gmail.com>

[ Upstream commit 19f953e7435644b81332dd632ba1b2d80b1e37af ]

In `do_fb_ioctl()` of fbmem.c, if cmd is FBIOPUT_VSCREENINFO, var will be
copied from user, then go through `fb_set_var()` and
`info->fbops->fb_check_var()` which could may be `pm2fb_check_var()`.
Along the path, `var->pixclock` won't be modified. This function checks
whether reciprocal of `var->pixclock` is too high. If `var->pixclock` is
zero, there will be a divide by zero error. So, it is necessary to check
whether denominator is zero to avoid crash. As this bug is found by
Syzkaller, logs are listed below.

divide error in pm2fb_check_var
Call Trace:
 <TASK>
 fb_set_var+0x367/0xeb0 drivers/video/fbdev/core/fbmem.c:1015
 do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1110
 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1189

Reported-by: Zheyu Ma <zheyuma97@gmail.com>
Signed-off-by: Letu Ren <fantasquex@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/video/fbdev/pm2fb.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/video/fbdev/pm2fb.c b/drivers/video/fbdev/pm2fb.c
index bd6c2f5f6095d..a5375b09415a6 100644
--- a/drivers/video/fbdev/pm2fb.c
+++ b/drivers/video/fbdev/pm2fb.c
@@ -614,6 +614,11 @@ static int pm2fb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
 		return -EINVAL;
 	}
 
+	if (!var->pixclock) {
+		DPRINTK("pixclock is zero\n");
+		return -EINVAL;
+	}
+
 	if (PICOS2KHZ(var->pixclock) > PM2_MAX_PIXCLOCK) {
 		DPRINTK("pixclock too high (%ldKHz)\n",
 			PICOS2KHZ(var->pixclock));
-- 
2.35.1

[PATCH AUTOSEL 4.14 8/8] fbdev: chipsfb: Add missing pci_disable_device() in chipsfb_pci_init()

[Sasha Levin]

From: Yang Yingliang <yangyingliang@huawei.com>

[ Upstream commit 07c55c9803dea748d17a054000cbf1913ce06399 ]

Add missing pci_disable_device() in error path in chipsfb_pci_init().

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/video/fbdev/chipsfb.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/video/fbdev/chipsfb.c b/drivers/video/fbdev/chipsfb.c
index 413b465e69d8e..7ca149ab86d20 100644
--- a/drivers/video/fbdev/chipsfb.c
+++ b/drivers/video/fbdev/chipsfb.c
@@ -432,6 +432,7 @@ static int chipsfb_pci_init(struct pci_dev *dp, const struct pci_device_id *ent)
  err_release_fb:
 	framebuffer_release(p);
  err_disable:
+	pci_disable_device(dp);
  err_out:
 	return rc;
 }
-- 
2.35.1