[PATCH] PCI/sysfs: Move to kstrtobool() to handle user input

[PATCH] PCI/sysfs: Move to kstrtobool() to handle user input

[Krzysztof Wilczyński]

A common use case for many PCI sysfs objects is to either enable some
functionality or trigger an action following a write to a given
attribute where the value is written would be simply either "1" or "0"
synonymous with either disabling or enabling something.

Parsing and validation of the input values are currently done using the
kstrtoul() function to convert anything in the string buffer into an
integer value - anything non-zero would be accepted as "enable" and zero
simply as "disable".

For a while now, the kernel offers another function called kstrtobool()
which was created to parse common user inputs into a boolean value, so
that a range of values such as "y", "n", "1", "0", "on" and "off"
handled in a case-insensitive manner would yield a boolean true or false
result accordingly after the input string has been parsed.

Thus, move to kstrtobool() over kstrtoul() as it's a better fit for
parsing user input, and it also implicitly offers a range check as only
a finite amount of possible input values will be considered as valid.

Where appropriate, move the user input parsing after checking for
whether the "CAP_SYS_ADMIN" flag is set, as it makes more sense to first
check whether the current user has the right permissions before
accepting any input from such user.

Related:

  commit d0f1fed29e6e ("Add a strtobool function matching semantics of existing in kernel equivalents")
  commit ef951599074b ("lib: move strtobool() to kstrtobool()")
  commit a81a5a17d44b ("lib: add "on"/"off" support to kstrtobool")
  commit 1404297ebf76 ("lib: update single-char callers of strtobool()")

Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
---
 drivers/pci/pci-sysfs.c | 105 +++++++++++++++++++---------------------
 1 file changed, 51 insertions(+), 54 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index beb8d1f4fafe..f777f358a177 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -63,13 +63,13 @@ static ssize_t broken_parity_status_store(struct device *dev,
 					  struct device_attribute *attr,
 					  const char *buf, size_t count)
 {
+	bool enable;
 	struct pci_dev *pdev = to_pci_dev(dev);
-	unsigned long val;
 
-	if (kstrtoul(buf, 0, &val) < 0)
+	if (kstrtobool(buf, &enable) < 0)
 		return -EINVAL;
 
-	pdev->broken_parity_status = !!val;
+	pdev->broken_parity_status = enable;
 
 	return count;
 }
@@ -271,21 +271,21 @@ static DEVICE_ATTR_RO(modalias);
 static ssize_t enable_store(struct device *dev, struct device_attribute *attr,
 			     const char *buf, size_t count)
 {
+	bool enable;
 	struct pci_dev *pdev = to_pci_dev(dev);
-	unsigned long val;
-	ssize_t result = kstrtoul(buf, 0, &val);
+	ssize_t result = 0;
 
-	if (result < 0)
-		return result;
-
-	/* this can crash the machine when done on the "wrong" device */
+	/* This can crash the machine when done on the "wrong" device. */
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
+	if (kstrtobool(buf, &enable) < 0)
+		return -EINVAL;
+
 	device_lock(dev);
 	if (dev->driver)
 		result = -EBUSY;
-	else if (val)
+	else if (enable)
 		result = pci_enable_device(pdev);
 	else if (pci_is_enabled(pdev))
 		pci_disable_device(pdev);
@@ -311,15 +311,14 @@ static ssize_t numa_node_store(struct device *dev,
 			       struct device_attribute *attr, const char *buf,
 			       size_t count)
 {
+	int node;
 	struct pci_dev *pdev = to_pci_dev(dev);
-	int node, ret;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	ret = kstrtoint(buf, 0, &node);
-	if (ret)
-		return ret;
+	if (kstrtoint(buf, 0, &node) < 0)
+		return -EINVAL;
 
 	if ((node < 0 && node != NUMA_NO_NODE) || node >= MAX_NUMNODES)
 		return -EINVAL;
@@ -374,48 +373,48 @@ static ssize_t msi_bus_show(struct device *dev, struct device_attribute *attr,
 static ssize_t msi_bus_store(struct device *dev, struct device_attribute *attr,
 			     const char *buf, size_t count)
 {
+	bool enable;
 	struct pci_dev *pdev = to_pci_dev(dev);
 	struct pci_bus *subordinate = pdev->subordinate;
-	unsigned long val;
-
-	if (kstrtoul(buf, 0, &val) < 0)
-		return -EINVAL;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
+	if (kstrtobool(buf, &enable) < 0)
+		return -EINVAL;
+
 	/*
 	 * "no_msi" and "bus_flags" only affect what happens when a driver
 	 * requests MSI or MSI-X.  They don't affect any drivers that have
 	 * already requested MSI or MSI-X.
 	 */
 	if (!subordinate) {
-		pdev->no_msi = !val;
+		pdev->no_msi = !enable;
 		pci_info(pdev, "MSI/MSI-X %s for future drivers\n",
-			 val ? "allowed" : "disallowed");
+			 enable ? "allowed" : "disallowed");
 		return count;
 	}
 
-	if (val)
+	if (enable)
 		subordinate->bus_flags &= ~PCI_BUS_FLAGS_NO_MSI;
 	else
 		subordinate->bus_flags |= PCI_BUS_FLAGS_NO_MSI;
 
 	dev_info(&subordinate->dev, "MSI/MSI-X %s for future drivers of devices on this bus\n",
-		 val ? "allowed" : "disallowed");
+		 enable ? "allowed" : "disallowed");
 	return count;
 }
 static DEVICE_ATTR_RW(msi_bus);
 
 static ssize_t rescan_store(struct bus_type *bus, const char *buf, size_t count)
 {
-	unsigned long val;
+	bool rescan;
 	struct pci_bus *b = NULL;
 
-	if (kstrtoul(buf, 0, &val) < 0)
+	if (kstrtobool(buf, &rescan) < 0)
 		return -EINVAL;
 
-	if (val) {
+	if (rescan) {
 		pci_lock_rescan_remove();
 		while ((b = pci_find_next_bus(b)) != NULL)
 			pci_rescan_bus(b);
@@ -443,13 +442,13 @@ static ssize_t dev_rescan_store(struct device *dev,
 				struct device_attribute *attr, const char *buf,
 				size_t count)
 {
-	unsigned long val;
+	bool rescan;
 	struct pci_dev *pdev = to_pci_dev(dev);
 
-	if (kstrtoul(buf, 0, &val) < 0)
+	if (kstrtobool(buf, &rescan) < 0)
 		return -EINVAL;
 
-	if (val) {
+	if (rescan) {
 		pci_lock_rescan_remove();
 		pci_rescan_bus(pdev->bus);
 		pci_unlock_rescan_remove();
@@ -462,12 +461,12 @@ static struct device_attribute dev_attr_dev_rescan = __ATTR(rescan, 0200, NULL,
 static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
 			    const char *buf, size_t count)
 {
-	unsigned long val;
+	bool remove;
 
-	if (kstrtoul(buf, 0, &val) < 0)
+	if (kstrtobool(buf, &remove) < 0)
 		return -EINVAL;
 
-	if (val && device_remove_file_self(dev, attr))
+	if (remove && device_remove_file_self(dev, attr))
 		pci_stop_and_remove_bus_device_locked(to_pci_dev(dev));
 	return count;
 }
@@ -478,13 +477,13 @@ static ssize_t bus_rescan_store(struct device *dev,
 				struct device_attribute *attr,
 				const char *buf, size_t count)
 {
-	unsigned long val;
+	bool rescan;
 	struct pci_bus *bus = to_pci_bus(dev);
 
-	if (kstrtoul(buf, 0, &val) < 0)
+	if (kstrtobool(buf, &rescan) < 0)
 		return -EINVAL;
 
-	if (val) {
+	if (rescan) {
 		pci_lock_rescan_remove();
 		if (!pci_is_root_bus(bus) && list_empty(&bus->devices))
 			pci_rescan_bus_bridge_resize(bus->self);
@@ -502,14 +501,14 @@ static ssize_t d3cold_allowed_store(struct device *dev,
 				    struct device_attribute *attr,
 				    const char *buf, size_t count)
 {
+	bool allowed;
 	struct pci_dev *pdev = to_pci_dev(dev);
-	unsigned long val;
 
-	if (kstrtoul(buf, 0, &val) < 0)
+	if (kstrtobool(buf, &allowed) < 0)
 		return -EINVAL;
 
-	pdev->d3cold_allowed = !!val;
-	if (pdev->d3cold_allowed)
+	pdev->d3cold_allowed = allowed;
+	if (allowed)
 		pci_d3cold_enable(pdev);
 	else
 		pci_d3cold_disable(pdev);
@@ -1257,12 +1256,13 @@ static ssize_t pci_write_rom(struct file *filp, struct kobject *kobj,
 			     struct bin_attribute *bin_attr, char *buf,
 			     loff_t off, size_t count)
 {
+	bool enable;
 	struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
 
-	if ((off ==  0) && (*buf == '0') && (count == 2))
-		pdev->rom_attr_enabled = 0;
-	else
-		pdev->rom_attr_enabled = 1;
+	if (kstrtobool(buf, &enable) < 0)
+		return -EINVAL;
+
+	pdev->rom_attr_enabled = enable;
 
 	return count;
 }
@@ -1337,23 +1337,20 @@ static const struct attribute_group pci_dev_rom_attr_group = {
 static ssize_t reset_store(struct device *dev, struct device_attribute *attr,
 			   const char *buf, size_t count)
 {
+	bool reset;
 	struct pci_dev *pdev = to_pci_dev(dev);
-	unsigned long val;
-	ssize_t result = kstrtoul(buf, 0, &val);
+	ssize_t result = 0;
 
-	if (result < 0)
-		return result;
-
-	if (val != 1)
+	if (kstrtobool(buf, &reset) < 0)
 		return -EINVAL;
 
-	pm_runtime_get_sync(dev);
-	result = pci_reset_function(pdev);
-	pm_runtime_put(dev);
-	if (result < 0)
-		return result;
+	if (reset) {
+		pm_runtime_get_sync(dev);
+		result = pci_reset_function(pdev);
+		pm_runtime_put(dev);
+	}
 
-	return count;
+	return result < 0 ? result : count;
 }
 static DEVICE_ATTR_WO(reset);
 
-- 
2.31.1