[PATCH v2 1/3] platform/x86: panasonic-laptop: Fix SINF array out of bounds accesses

[Hans de Goede <hdegoede@redhat.com>]

The panasonic laptop code in various places uses the SINF array with index
values of 0 - SINF_CUR_BRIGHT(0x0d) without checking that the SINF array
is big enough.

Not all panasonic laptops have this many SINF array entries, for example
the Toughbook CF-18 model only has 10 SINF array entries. So it only
supports the AC+DC brightness entries and mute.

Check that the SINF array has a minimum size which covers all AC+DC
brightness entries and refuse to load if the SINF array is smaller.

For higher SINF indexes hide the sysfs attributes when the SINF array
does not contain an entry for that attribute, avoiding show()/store()
accessing the array out of bounds and add bounds checking to the probe()
and resume() code accessing these.

Fixes: e424fb8cc4e6 ("panasonic-laptop: avoid overflow in acpi_pcc_hotkey_add()")
Cc: stable@vger.kernel.org
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v2:
- Some panasonic laptops have only 10 SINF entries. Change the required
  minimum SQTY to SQTY > SINF_DC_CUR_BRIGHT and avoid the driver accessing
  higher indexes by adding num_sifr checks.
---
 drivers/platform/x86/panasonic-laptop.c | 49 ++++++++++++++++++++-----
 1 file changed, 39 insertions(+), 10 deletions(-)

diff --git a/drivers/platform/x86/panasonic-laptop.c b/drivers/platform/x86/panasonic-laptop.c
index cf845ee1c7b1..39044119d2a6 100644
--- a/drivers/platform/x86/panasonic-laptop.c
+++ b/drivers/platform/x86/panasonic-laptop.c
@@ -773,6 +773,24 @@ static DEVICE_ATTR_RW(dc_brightness);
 static DEVICE_ATTR_RW(current_brightness);
 static DEVICE_ATTR_RW(cdpower);
 
+static umode_t pcc_sysfs_is_visible(struct kobject *kobj, struct attribute *attr, int idx)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct acpi_device *acpi = to_acpi_device(dev);
+	struct pcc_acpi *pcc = acpi_driver_data(acpi);
+
+	if (attr == &dev_attr_mute.attr)
+		return (pcc->num_sifr > SINF_MUTE) ? attr->mode : 0;
+
+	if (attr == &dev_attr_eco_mode.attr)
+		return (pcc->num_sifr > SINF_ECO_MODE) ? attr->mode : 0;
+
+	if (attr == &dev_attr_current_brightness.attr)
+		return (pcc->num_sifr > SINF_CUR_BRIGHT) ? attr->mode : 0;
+
+	return attr->mode;
+}
+
 static struct attribute *pcc_sysfs_entries[] = {
 	&dev_attr_numbatt.attr,
 	&dev_attr_lcdtype.attr,
@@ -787,8 +805,9 @@ static struct attribute *pcc_sysfs_entries[] = {
 };
 
 static const struct attribute_group pcc_attr_group = {
-	.name	= NULL,		/* put in device directory */
-	.attrs	= pcc_sysfs_entries,
+	.name		= NULL,		/* put in device directory */
+	.attrs		= pcc_sysfs_entries,
+	.is_visible	= pcc_sysfs_is_visible,
 };
 
 
@@ -941,12 +960,15 @@ static int acpi_pcc_hotkey_resume(struct device *dev)
 	if (!pcc)
 		return -EINVAL;
 
-	acpi_pcc_write_sset(pcc, SINF_MUTE, pcc->mute);
-	acpi_pcc_write_sset(pcc, SINF_ECO_MODE, pcc->eco_mode);
+	if (pcc->num_sifr > SINF_MUTE)
+		acpi_pcc_write_sset(pcc, SINF_MUTE, pcc->mute);
+	if (pcc->num_sifr > SINF_ECO_MODE)
+		acpi_pcc_write_sset(pcc, SINF_ECO_MODE, pcc->eco_mode);
 	acpi_pcc_write_sset(pcc, SINF_STICKY_KEY, pcc->sticky_key);
 	acpi_pcc_write_sset(pcc, SINF_AC_CUR_BRIGHT, pcc->ac_brightness);
 	acpi_pcc_write_sset(pcc, SINF_DC_CUR_BRIGHT, pcc->dc_brightness);
-	acpi_pcc_write_sset(pcc, SINF_CUR_BRIGHT, pcc->current_brightness);
+	if (pcc->num_sifr > SINF_CUR_BRIGHT)
+		acpi_pcc_write_sset(pcc, SINF_CUR_BRIGHT, pcc->current_brightness);
 
 	return 0;
 }
@@ -963,8 +985,12 @@ static int acpi_pcc_hotkey_add(struct acpi_device *device)
 
 	num_sifr = acpi_pcc_get_sqty(device);
 
-	if (num_sifr < 0 || num_sifr > 255) {
-		pr_err("num_sifr out of range");
+	/*
+	 * pcc->sinf is expected to at least have the AC+DC brightness entries.
+	 * Accesses to higher SINF entries are checked against num_sifr.
+	 */
+	if (num_sifr <= SINF_DC_CUR_BRIGHT || num_sifr > 255) {
+		pr_err("num_sifr %d out of range %d - 255\n", num_sifr, SINF_DC_CUR_BRIGHT + 1);
 		return -ENODEV;
 	}
 
@@ -1020,11 +1046,14 @@ static int acpi_pcc_hotkey_add(struct acpi_device *device)
 	acpi_pcc_write_sset(pcc, SINF_STICKY_KEY, 0);
 	pcc->sticky_key = 0;
 
-	pcc->eco_mode = pcc->sinf[SINF_ECO_MODE];
-	pcc->mute = pcc->sinf[SINF_MUTE];
 	pcc->ac_brightness = pcc->sinf[SINF_AC_CUR_BRIGHT];
 	pcc->dc_brightness = pcc->sinf[SINF_DC_CUR_BRIGHT];
-	pcc->current_brightness = pcc->sinf[SINF_CUR_BRIGHT];
+	if (pcc->num_sifr > SINF_MUTE)
+		pcc->mute = pcc->sinf[SINF_MUTE];
+	if (pcc->num_sifr > SINF_ECO_MODE)
+		pcc->eco_mode = pcc->sinf[SINF_ECO_MODE];
+	if (pcc->num_sifr > SINF_CUR_BRIGHT)
+		pcc->current_brightness = pcc->sinf[SINF_CUR_BRIGHT];
 
 	/* add sysfs attributes */
 	result = sysfs_create_group(&device->dev.kobj, &pcc_attr_group);
-- 
2.46.0