[PATCH 5.4 104/214] hwmon: (nct7904) Correct divide by 0

Greg Kroah-Hartman
2020-09-01T16:35:24Z

From: Jason Baron <jbaron@akamai.com>

[ Upstream commit 8aebbbb2d573d0b4afc08b90ac7d73dba2d9da97 ]

We hit a kernel panic due to a divide by 0 in nct7904_read_fan() for
the hwmon_fan_min case. Extend the check to hwmon_fan_input case as well
for safety.

[ 1656.545650] divide error: 0000 [#1] SMP PTI
[ 1656.545779] CPU: 12 PID: 18010 Comm: sensors Not tainted 5.4.47 #1
[ 1656.546065] RIP: 0010:nct7904_read+0x1e9/0x510 [nct7904]
...
[ 1656.546549] RAX: 0000000000149970 RBX: ffffbd6b86bcbe08 RCX: 0000000000000000
...
[ 1656.547548] Call Trace:
[ 1656.547665] hwmon_attr_show+0x32/0xd0 [hwmon]
[ 1656.547783] dev_attr_show+0x18/0x50
[ 1656.547898] sysfs_kf_seq_show+0x99/0x120
[ 1656.548013] seq_read+0xd8/0x3e0
[ 1656.548127] vfs_read+0x89/0x130
[ 1656.548234] ksys_read+0x7d/0xb0
[ 1656.548342] do_syscall_64+0x48/0x110
[ 1656.548451] entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: d65a5102a99f5 ("hwmon: (nct7904) Convert to use new hwmon registration API")
Signed-off-by: Jason Baron <jbaron@akamai.com>
Link: https://lore.kernel.org/r/1598026814-2604-1-git-send-email-jbaron@akamai.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/hwmon/nct7904.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/nct7904.c b/drivers/hwmon/nct7904.c
index dfb122b5e1b76..b812b199e5e5b 100644
--- a/drivers/hwmon/nct7904.c
+++ b/drivers/hwmon/nct7904.c
@@ -197,7 +197,7 @@ static int nct7904_read_fan(struct device *dev, u32 attr, int channel,
if (ret < 0)
return ret;
cnt = ((ret & 0xff00) >> 3) | (ret & 0x1f);
- if (cnt == 0x1fff)
+ if (cnt == 0 || cnt == 0x1fff)
rpm = 0;
else
rpm = 1350000 / cnt;
@@ -209,7 +209,7 @@ static int nct7904_read_fan(struct device *dev, u32 attr, int channel,
if (ret < 0)
return ret;
cnt = ((ret & 0xff00) >> 3) | (ret & 0x1f);
- if (cnt == 0x1fff)
+ if (cnt == 0 || cnt == 0x1fff)
rpm = 0;
else
rpm = 1350000 / cnt;
--
2.25.1