Re: [PATCH 1/1] mtd: spi-nor: core: Prevent oops during driver removal with active read or write operations

[Dan Carpenter <dan.carpenter@linaro.org>]

Hi,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/khairul-anuar-romli-altera-com/mtd-spi-nor-core-Prevent-oops-during-driver-removal-with-active-read-or-write-operations/20250709-103107
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git spi-nor/next
patch link:    https://lore.kernel.org/r/e439e6b85e650a91607a1d02d5d432d096363315.1752024352.git.khairul.anuar.romli%40altera.com
patch subject: [PATCH 1/1] mtd: spi-nor: core: Prevent oops during driver removal with active read or write operations
config: i386-randconfig-141-20250711 (https://download.01.org/0day-ci/archive/20250711/202507110922.btkgvYrn-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202507110922.btkgvYrn-lkp@intel.com/

smatch warnings:
drivers/mtd/spi-nor/core.c:3216 spi_nor_get_device() warn: variable dereferenced before check 'dev' (see line 3213)
drivers/mtd/spi-nor/core.c:3216 spi_nor_get_device() warn: variable dereferenced before check 'dev->driver' (see line 3213)

vim +/dev +3216 drivers/mtd/spi-nor/core.c

be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3202  static int spi_nor_get_device(struct mtd_info *mtd)
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3203  {
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3204  	struct mtd_info *master = mtd_get_master(mtd);
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3205  	struct spi_nor *nor = mtd_to_spi_nor(master);
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3206  	struct device *dev;
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3207  
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3208  	if (nor->spimem)
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3209  		dev = nor->spimem->spi->controller->dev.parent;
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3210  	else
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3211  		dev = nor->dev;
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3212  
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01 @3213  	if (!try_module_get(dev->driver->owner))
                                                                                                    ^^^^^^^^^^^^^^^^^^
Dereference

be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3214  		return -ENODEV;
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3215  
240522762fc4bc drivers/mtd/spi-nor/core.c    kromli     2025-07-09 @3216  	if (!dev && !dev->driver && !dev->driver->owner)
                                                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
These checks are done too late.  Also missing module put.


240522762fc4bc drivers/mtd/spi-nor/core.c    kromli     2025-07-09  3217  		return -EINVAL;
240522762fc4bc drivers/mtd/spi-nor/core.c    kromli     2025-07-09  3218  
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3219  	return 0;
be94215be1ab19 drivers/mtd/spi-nor/core.c    Xiang Chen 2021-04-01  3220  }

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki


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