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Subject[PATCH] w1: keep balance of mutex locks and refcnts
Date
w1_therm_eeprom() and w1_DS18B20_precision() decrement THERM_REFCNT
on error paths, while they did not increment it yet.

read_therm() unlocks bus mutex on some error paths,
while it is not acquired.

The patch makes sure all the functions keep the balance in usage of
the mutex and the THERM_REFCNT.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
---
drivers/w1/slaves/w1_therm.c | 37 ++++++++++++++++---------------------
1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index 259525c3382a..fcd4d52e56e3 100644
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -270,11 +270,11 @@ static inline int w1_therm_eeprom(struct device *device)

ret = mutex_lock_interruptible(&dev->bus_mutex);
if (ret != 0)
- goto post_unlock;
+ return ret;

if (!sl->family_data) {
- ret = -ENODEV;
- goto pre_unlock;
+ mutex_unlock(&dev->bus_mutex);
+ return -ENODEV;
}

/* prevent the slave from going away in sleep */
@@ -326,7 +326,6 @@ static inline int w1_therm_eeprom(struct device *device)

pre_unlock:
mutex_unlock(&dev->bus_mutex);
-
post_unlock:
atomic_dec(THERM_REFCNT(family_data));
return ret;
@@ -350,16 +349,16 @@ static inline int w1_DS18B20_precision(struct device *device, int val)

if (val > 12 || val < 9) {
pr_warn("Unsupported precision\n");
- return -1;
+ return -EINVAL;
}

ret = mutex_lock_interruptible(&dev->bus_mutex);
if (ret != 0)
- goto post_unlock;
+ return ret;

if (!sl->family_data) {
- ret = -ENODEV;
- goto pre_unlock;
+ mutex_unlock(&dev->bus_mutex);
+ return -ENODEV;
}

/* prevent the slave from going away in sleep */
@@ -411,10 +410,7 @@ static inline int w1_DS18B20_precision(struct device *device, int val)
}
}

-pre_unlock:
mutex_unlock(&dev->bus_mutex);
-
-post_unlock:
atomic_dec(THERM_REFCNT(family_data));
return ret;
}
@@ -492,11 +488,11 @@ static ssize_t read_therm(struct device *device,

ret = mutex_lock_interruptible(&dev->bus_mutex);
if (ret != 0)
- goto error;
+ return ret;

if (!family_data) {
- ret = -ENODEV;
- goto mt_unlock;
+ mutex_unlock(&dev->bus_mutex);
+ return -ENODEV;
}

/* prevent the slave from going away in sleep */
@@ -532,17 +528,17 @@ static ssize_t read_therm(struct device *device,
sleep_rem = msleep_interruptible(tm);
if (sleep_rem != 0) {
ret = -EINTR;
- goto dec_refcnt;
+ goto post_unlock;
}

ret = mutex_lock_interruptible(&dev->bus_mutex);
if (ret != 0)
- goto dec_refcnt;
+ goto post_unlock;
} else if (!w1_strong_pullup) {
sleep_rem = msleep_interruptible(tm);
if (sleep_rem != 0) {
ret = -EINTR;
- goto dec_refcnt;
+ goto pre_unlock;
}
}

@@ -567,11 +563,10 @@ static ssize_t read_therm(struct device *device,
break;
}

-dec_refcnt:
- atomic_dec(THERM_REFCNT(family_data));
-mt_unlock:
+pre_unlock:
mutex_unlock(&dev->bus_mutex);
-error:
+post_unlock:
+ atomic_dec(THERM_REFCNT(family_data));
return ret;
}

--
2.7.4
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