[PATCH AUTOSEL 4.20 34/77] drivers: thermal: int340x_thermal: Fix sysfs race condition

Sasha Levin
2019-02-15T02:09:59Z

From: Aaron Hill <aa1ronham@gmail.com>

[ Upstream commit 129699bb8c7572106b5bbb2407c2daee4727ccad ]

Changes since V1:
* Use dev_info instead of printk
* Use dev_warn instead of BUG_ON

Previously, sysfs_create_group was called before all initialization had
fully run - specifically, before pci_set_drvdata was called. Since the
sysctl group is visible to userspace as soon as sysfs_create_group
returns, a small window of time existed during which a process could read
from an uninitialized/partially-initialized device.

This commit moves the creation of the sysctl group to after all
initialized is completed. This ensures that it's impossible for
userspace to read from a sysctl file before initialization has fully
completed.

To catch any future regressions, I've added a check to ensure
that proc_thermal_emum_mode is never PROC_THERMAL_NONE when a process
tries to read from a sysctl file. Previously, the aforementioned race
condition could result in the 'else' branch
running while PROC_THERMAL_NONE was set,
leading to a null pointer deference.

Signed-off-by: Aaron Hill <aa1ronham@gmail.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../processor_thermal_device.c | 28 ++++++++++---------
1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/thermal/int340x_thermal/processor_thermal_device.c b/drivers/thermal/int340x_thermal/processor_thermal_device.c
index 8e0f665cf06f..8e1cf4d789be 100644
--- a/drivers/thermal/int340x_thermal/processor_thermal_device.c
+++ b/drivers/thermal/int340x_thermal/processor_thermal_device.c
@@ -84,7 +84,12 @@ static ssize_t power_limit_##index##_##suffix##_show(struct device *dev, \
struct pci_dev *pci_dev; \
struct platform_device *pdev; \
struct proc_thermal_device *proc_dev; \
-\
+ \
+ if (proc_thermal_emum_mode == PROC_THERMAL_NONE) { \
+ dev_warn(dev, "Attempted to get power limit before device was initialized!\n"); \
+ return 0; \
+ } \
+ \
if (proc_thermal_emum_mode == PROC_THERMAL_PLATFORM_DEV) { \
pdev = to_platform_device(dev); \
proc_dev = platform_get_drvdata(pdev); \
@@ -298,11 +303,6 @@ static int proc_thermal_add(struct device *dev,
*priv = proc_priv;

ret = proc_thermal_read_ppcc(proc_priv);
- if (!ret) {
- ret = sysfs_create_group(&dev->kobj,
- &power_limit_attribute_group);
-
- }
if (ret)
return ret;

@@ -316,8 +316,7 @@ static int proc_thermal_add(struct device *dev,

proc_priv->int340x_zone = int340x_thermal_zone_add(adev, ops);
if (IS_ERR(proc_priv->int340x_zone)) {
- ret = PTR_ERR(proc_priv->int340x_zone);
- goto remove_group;
+ return PTR_ERR(proc_priv->int340x_zone);
} else
ret = 0;

@@ -331,9 +330,6 @@ static int proc_thermal_add(struct device *dev,

remove_zone:
int340x_thermal_zone_remove(proc_priv->int340x_zone);
-remove_group:
- sysfs_remove_group(&proc_priv->dev->kobj,
- &power_limit_attribute_group);

return ret;
}
@@ -364,7 +360,10 @@ static int int3401_add(struct platform_device *pdev)
platform_set_drvdata(pdev, proc_priv);
proc_thermal_emum_mode = PROC_THERMAL_PLATFORM_DEV;

- return 0;
+ dev_info(&pdev->dev, "Creating sysfs group for PROC_THERMAL_PLATFORM_DEV\n");
+
+ return sysfs_create_group(&pdev->dev.kobj,
+ &power_limit_attribute_group);
}

static int int3401_remove(struct platform_device *pdev)
@@ -441,7 +440,10 @@ static int proc_thermal_pci_probe(struct pci_dev *pdev,
dev_err(&pdev->dev, "No auxiliary DTSs enabled\n");
}

- return 0;
+ dev_info(&pdev->dev, "Creating sysfs group for PROC_THERMAL_PCI\n");
+
+ return sysfs_create_group(&pdev->dev.kobj,
+ &power_limit_attribute_group);
}

static void proc_thermal_pci_remove(struct pci_dev *pdev)
--
2.19.1