linux-kernel - drivers/rtc/rtc-nct3018y.c:112 nct3018y_get_alarm_mode() error: we previously assumed 'alarm

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Message-ID: <6ac4b277-b8ff-4ffa-8786-80f7709155e2@kili.mountain>
Date:   Wed, 17 May 2023 20:34:21 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     oe-kbuild@...ts.linux.dev, Mia Lin <mimi05633@...il.com>
Cc:     lkp@...el.com, oe-kbuild-all@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: drivers/rtc/rtc-nct3018y.c:112 nct3018y_get_alarm_mode() error: we
 previously assumed 'alarm_enable' could be null (see line 96)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   f1fcbaa18b28dec10281551dfe6ed3a3ed80e3d6
commit: 5adbaed16cc63542057627642d2414f603f2db69 rtc: Add NCT3018Y real time clock driver
config: microblaze-randconfig-m031-20230517
compiler: microblaze-linux-gcc (GCC) 12.1.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@...el.com>
| Reported-by: Dan Carpenter <error27@...il.com>
| Closes: https://lore.kernel.org/r/202305180042.DEzW1pSd-lkp@intel.com/

smatch warnings:
drivers/rtc/rtc-nct3018y.c:112 nct3018y_get_alarm_mode() error: we previously assumed 'alarm_enable' could be null (see line 96)
drivers/rtc/rtc-nct3018y.c:112 nct3018y_get_alarm_mode() error: we previously assumed 'alarm_flag' could be null (see line 104)

vim +/alarm_enable +112 drivers/rtc/rtc-nct3018y.c

5adbaed16cc635 Mia Lin 2022-07-13   91  static int nct3018y_get_alarm_mode(struct i2c_client *client, unsigned char *alarm_enable,
5adbaed16cc635 Mia Lin 2022-07-13   92  				   unsigned char *alarm_flag)
5adbaed16cc635 Mia Lin 2022-07-13   93  {
5adbaed16cc635 Mia Lin 2022-07-13   94  	int flags;
5adbaed16cc635 Mia Lin 2022-07-13   95  
5adbaed16cc635 Mia Lin 2022-07-13  @96  	if (alarm_enable) {
                                                    ^^^^^^^^^^^^
If these are NULL

5adbaed16cc635 Mia Lin 2022-07-13   97  		dev_dbg(&client->dev, "%s:NCT3018Y_REG_CTRL\n", __func__);
5adbaed16cc635 Mia Lin 2022-07-13   98  		flags =  i2c_smbus_read_byte_data(client, NCT3018Y_REG_CTRL);
5adbaed16cc635 Mia Lin 2022-07-13   99  		if (flags < 0)
5adbaed16cc635 Mia Lin 2022-07-13  100  			return flags;
5adbaed16cc635 Mia Lin 2022-07-13  101  		*alarm_enable = flags & NCT3018Y_BIT_AIE;
5adbaed16cc635 Mia Lin 2022-07-13  102  	}
5adbaed16cc635 Mia Lin 2022-07-13  103  
5adbaed16cc635 Mia Lin 2022-07-13 @104  	if (alarm_flag) {
                                                    ^^^^^^^^^^

5adbaed16cc635 Mia Lin 2022-07-13  105  		dev_dbg(&client->dev, "%s:NCT3018Y_REG_ST\n", __func__);
5adbaed16cc635 Mia Lin 2022-07-13  106  		flags =  i2c_smbus_read_byte_data(client, NCT3018Y_REG_ST);
5adbaed16cc635 Mia Lin 2022-07-13  107  		if (flags < 0)
5adbaed16cc635 Mia Lin 2022-07-13  108  			return flags;
5adbaed16cc635 Mia Lin 2022-07-13  109  		*alarm_flag = flags & NCT3018Y_BIT_AF;
5adbaed16cc635 Mia Lin 2022-07-13  110  	}
5adbaed16cc635 Mia Lin 2022-07-13  111  
5adbaed16cc635 Mia Lin 2022-07-13 @112  	dev_dbg(&client->dev, "%s:alarm_enable:%x alarm_flag:%x\n",
5adbaed16cc635 Mia Lin 2022-07-13  113  		__func__, *alarm_enable, *alarm_flag);
                                                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^
The debug code will crash.

5adbaed16cc635 Mia Lin 2022-07-13  114  
5adbaed16cc635 Mia Lin 2022-07-13  115  	return 0;
5adbaed16cc635 Mia Lin 2022-07-13  116  }

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