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hwmon: (pmbus/isl68137) Add mutex protection for AVS enable sysfs attributes

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The custom avs0_enable and avs1_enable sysfs attributes access PMBus
registers through the exported API helpers (pmbus_read_byte_data,
pmbus_read_word_data, pmbus_write_word_data, pmbus_update_byte_data)
without holding the PMBus update_lock mutex. These exported helpers do
not acquire the mutex internally, unlike the core's internal callers
which hold the lock before invoking them.

The store callback is especially vulnerable: it performs a multi-step
read-modify-write sequence (read VOUT_COMMAND, write VOUT_COMMAND, then
update OPERATION) where concurrent access from another thread could
interleave and corrupt the register state.

Add pmbus_lock_interruptible()/pmbus_unlock() around both the show and
store callbacks to serialize PMBus register access with the rest of the
driver.

Fixes: 038a9c3d1e ("hwmon: (pmbus/isl68137) Add driver for Intersil ISL68137 PWM Controller")
Cc: stable@vger.kernel.org
Signed-off-by: Sanman Pradhan <psanman@juniper.net>
Link: https://lore.kernel.org/r/20260319173055.125271-3-sanman.pradhan@hpe.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Sanman Pradhan 2026-03-19 17:31:29 +00:00 committed by Guenter Roeck
parent f7e775c469
commit 3075a3951f
1 changed files with 18 additions and 3 deletions
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21
drivers/hwmon/pmbus/isl68137.c
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@ -96,7 +96,15 @@ static ssize_t isl68137_avs_enable_show_page(struct i2c_client *client,
int page,
char *buf)
{
int val = pmbus_read_byte_data(client, page, PMBUS_OPERATION);
int val;
val = pmbus_lock_interruptible(client);
if (val)
return val;
val = pmbus_read_byte_data(client, page, PMBUS_OPERATION);
pmbus_unlock(client);
if (val < 0)
return val;
@ -118,6 +126,10 @@ static ssize_t isl68137_avs_enable_store_page(struct i2c_client *client,
op_val = result ? ISL68137_VOUT_AVS : 0;
rc = pmbus_lock_interruptible(client);
if (rc)
return rc;
/*
* Writes to VOUT setpoint over AVSBus will persist after the VRM is
* switched to PMBus control. Switching back to AVSBus control
@ -129,17 +141,20 @@ static ssize_t isl68137_avs_enable_store_page(struct i2c_client *client,
rc = pmbus_read_word_data(client, page, 0xff,
PMBUS_VOUT_COMMAND);
if (rc < 0)
return rc;
goto unlock;
rc = pmbus_write_word_data(client, page, PMBUS_VOUT_COMMAND,
rc);
if (rc < 0)
return rc;
goto unlock;
}
rc = pmbus_update_byte_data(client, page, PMBUS_OPERATION,
ISL68137_VOUT_AVS, op_val);
unlock:
pmbus_unlock(client);
return (rc < 0) ? rc : count;
}