From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Letu Ren <fantasquex@gmail.com>, Zheyu Ma <zheyuma97@gmail.com>,
Helge Deller <deller@gmx.de>, Sasha Levin <sashal@kernel.org>,
baihaowen@meizu.com, linux-fbdev@vger.kernel.org,
dri-devel@lists.freedesktop.org
Subject: [PATCH AUTOSEL 5.15 20/23] fbdev: fb_pm2fb: Avoid potential divide by zero error
Date: Tue, 30 Aug 2022 13:21:37 -0400 [thread overview]
Message-ID: <20220830172141.581086-20-sashal@kernel.org> (raw)
In-Reply-To: <20220830172141.581086-1-sashal@kernel.org>
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 c68725eebee3b..cbcf112c88d30 100644
--- a/drivers/video/fbdev/pm2fb.c
+++ b/drivers/video/fbdev/pm2fb.c
@@ -617,6 +617,11 @@ 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
next parent reply other threads:[~2022-08-30 17:26 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220830172141.581086-1-sashal@kernel.org>
2022-08-30 17:21 ` Sasha Levin [this message]
2022-08-30 17:21 ` [PATCH AUTOSEL 5.15 21/23] fbdev: fbcon: Destroy mutex on freeing struct fb_info Sasha Levin
2022-08-30 17:21 ` [PATCH AUTOSEL 5.15 22/23] fbdev: chipsfb: Add missing pci_disable_device() in chipsfb_pci_init() Sasha Levin
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