[PATCH AUTOSEL 4.19 032/237] w1: IAD Register is yet readable trough iad sys file. Fix snprintf (%u for unsigned, count for max size).

Sasha Levin
2019-11-16T16:26:50Z

From: Julien Folly <julien.folly@gmail.com>

[ Upstream commit 6eaafbb6998e999467cf78a76e155ee00e372b14 ]

IAD Register is yet readable trough the "iad" sys file.

A write to the "iad" sys file enables or disables the current
measurement, but it was not possible to get the measured value by
reading it.
Fix: %u in snprintf for unsigned values (vdd and vad)
Fix: Avoid possibles overflows (Usage of the 'count' variables)

Signed-off-by: Julien Folly <julien.folly@gmail.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/w1/slaves/w1_ds2438.c | 66 +++++++++++++++++++++++++++--------
1 file changed, 52 insertions(+), 14 deletions(-)

diff --git a/drivers/w1/slaves/w1_ds2438.c b/drivers/w1/slaves/w1_ds2438.c
index bf641a191d077..7c4e33dbee4d5 100644
--- a/drivers/w1/slaves/w1_ds2438.c
+++ b/drivers/w1/slaves/w1_ds2438.c
@@ -186,8 +186,8 @@ static int w1_ds2438_change_config_bit(struct w1_slave *sl, u8 mask, u8 value)
return -1;
}

-static uint16_t w1_ds2438_get_voltage(struct w1_slave *sl,
- int adc_input, uint16_t *voltage)
+static int w1_ds2438_get_voltage(struct w1_slave *sl,
+ int adc_input, uint16_t *voltage)
{
unsigned int retries = W1_DS2438_RETRIES;
u8 w1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/];
@@ -235,6 +235,25 @@ static uint16_t w1_ds2438_get_voltage(struct w1_slave *sl,
return ret;
}

+static int w1_ds2438_get_current(struct w1_slave *sl, int16_t *voltage)
+{
+ u8 w1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/];
+ int ret;
+
+ mutex_lock(&sl->master->bus_mutex);
+
+ if (w1_ds2438_get_page(sl, 0, w1_buf) == 0) {
+ /* The voltage measured across current sense resistor RSENS. */
+ *voltage = (((int16_t) w1_buf[DS2438_CURRENT_MSB]) << 8) | ((int16_t) w1_buf[DS2438_CURRENT_LSB]);
+ ret = 0;
+ } else
+ ret = -1;
+
+ mutex_unlock(&sl->master->bus_mutex);
+
+ return ret;
+}
+
static ssize_t iad_write(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
@@ -257,6 +276,27 @@ static ssize_t iad_write(struct file *filp, struct kobject *kobj,
return ret;
}

+static ssize_t iad_read(struct file *filp, struct kobject *kobj,
+ struct bin_attribute *bin_attr, char *buf,
+ loff_t off, size_t count)
+{
+ struct w1_slave *sl = kobj_to_w1_slave(kobj);
+ int ret;
+ int16_t voltage;
+
+ if (off != 0)
+ return 0;
+ if (!buf)
+ return -EINVAL;
+
+ if (w1_ds2438_get_current(sl, &voltage) == 0) {
+ ret = snprintf(buf, count, "%i\n", voltage);
+ } else
+ ret = -EIO;
+
+ return ret;
+}
+
static ssize_t page0_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
@@ -272,9 +312,13 @@ static ssize_t page0_read(struct file *filp, struct kobject *kobj,

mutex_lock(&sl->master->bus_mutex);

+ /* Read no more than page0 size */
+ if (count > DS2438_PAGE_SIZE)
+ count = DS2438_PAGE_SIZE;
+
if (w1_ds2438_get_page(sl, 0, w1_buf) == 0) {
- memcpy(buf, &w1_buf, DS2438_PAGE_SIZE);
- ret = DS2438_PAGE_SIZE;
+ memcpy(buf, &w1_buf, count);
+ ret = count;
} else
ret = -EIO;

@@ -289,7 +333,6 @@ static ssize_t temperature_read(struct file *filp, struct kobject *kobj,
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
int ret;
- ssize_t c = PAGE_SIZE;
int16_t temp;

if (off != 0)
@@ -298,8 +341,7 @@ static ssize_t temperature_read(struct file *filp, struct kobject *kobj,
return -EINVAL;

if (w1_ds2438_get_temperature(sl, &temp) == 0) {
- c -= snprintf(buf + PAGE_SIZE - c, c, "%d\n", temp);
- ret = PAGE_SIZE - c;
+ ret = snprintf(buf, count, "%i\n", temp);
} else
ret = -EIO;

@@ -312,7 +354,6 @@ static ssize_t vad_read(struct file *filp, struct kobject *kobj,
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
int ret;
- ssize_t c = PAGE_SIZE;
uint16_t voltage;

if (off != 0)
@@ -321,8 +362,7 @@ static ssize_t vad_read(struct file *filp, struct kobject *kobj,
return -EINVAL;

if (w1_ds2438_get_voltage(sl, DS2438_ADC_INPUT_VAD, &voltage) == 0) {
- c -= snprintf(buf + PAGE_SIZE - c, c, "%d\n", voltage);
- ret = PAGE_SIZE - c;
+ ret = snprintf(buf, count, "%u\n", voltage);
} else
ret = -EIO;

@@ -335,7 +375,6 @@ static ssize_t vdd_read(struct file *filp, struct kobject *kobj,
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
int ret;
- ssize_t c = PAGE_SIZE;
uint16_t voltage;

if (off != 0)
@@ -344,15 +383,14 @@ static ssize_t vdd_read(struct file *filp, struct kobject *kobj,
return -EINVAL;

if (w1_ds2438_get_voltage(sl, DS2438_ADC_INPUT_VDD, &voltage) == 0) {
- c -= snprintf(buf + PAGE_SIZE - c, c, "%d\n", voltage);
- ret = PAGE_SIZE - c;
+ ret = snprintf(buf, count, "%u\n", voltage);
} else
ret = -EIO;

return ret;
}

-static BIN_ATTR(iad, S_IRUGO | S_IWUSR | S_IWGRP, NULL, iad_write, 1);
+static BIN_ATTR(iad, S_IRUGO | S_IWUSR | S_IWGRP, iad_read, iad_write, 0);
static BIN_ATTR_RO(page0, DS2438_PAGE_SIZE);
static BIN_ATTR_RO(temperature, 0/* real length varies */);
static BIN_ATTR_RO(vad, 0/* real length varies */);
--
2.20.1