linux-kernel - drivers/remoteproc/pru_rproc.c:341 pru_rproc_set_ctable() warn: variable dereferenced before IS

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Date:   Sat, 29 Jul 2023 00:07:18 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     oe-kbuild@...ts.linux.dev, Simon Horman <horms@...nel.org>
Cc:     lkp@...el.com, oe-kbuild-all@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: drivers/remoteproc/pru_rproc.c:341 pru_rproc_set_ctable() warn:
 variable dereferenced before IS_ERR check 'rproc' (see line 335)

Hi Simon,

FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   f837f0a3c94882a29e38ff211a36c1c8a0f07804
commit: e752f9b924a1fd1afcf36e51b03dfa9c3096a3bd soc: ti: pruss: Allow compile-testing
config: csky-randconfig-m041-20230727 (https://download.01.org/0day-ci/archive/20230729/202307290417.hrgfPCcg-lkp@intel.com/config)
compiler: csky-linux-gcc (GCC) 12.3.0
reproduce: (https://download.01.org/0day-ci/archive/20230729/202307290417.hrgfPCcg-lkp@intel.com/reproduce)

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@...el.com>
| Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
| Closes: https://lore.kernel.org/r/202307290417.hrgfPCcg-lkp@intel.com/

smatch warnings:
drivers/remoteproc/pru_rproc.c:341 pru_rproc_set_ctable() warn: variable dereferenced before IS_ERR check 'rproc' (see line 335)

vim +/rproc +341 drivers/remoteproc/pru_rproc.c

102853400321bae Roger Quadros   2023-01-06  333  int pru_rproc_set_ctable(struct rproc *rproc, enum pru_ctable_idx c, u32 addr)
102853400321bae Roger Quadros   2023-01-06  334  {
102853400321bae Roger Quadros   2023-01-06 @335  	struct pru_rproc *pru = rproc->priv;
                                                                                ^^^^^^^^^^^^
Dereference

102853400321bae Roger Quadros   2023-01-06  336  	unsigned int reg;
102853400321bae Roger Quadros   2023-01-06  337  	u32 mask, set;
102853400321bae Roger Quadros   2023-01-06  338  	u16 idx;
102853400321bae Roger Quadros   2023-01-06  339  	u16 idx_mask;
102853400321bae Roger Quadros   2023-01-06  340  
102853400321bae Roger Quadros   2023-01-06 @341  	if (IS_ERR_OR_NULL(rproc))
102853400321bae Roger Quadros   2023-01-06  342  		return -EINVAL;

Checked too late.  Also ideally it would be:

	if (IS_ERR_OR_NULL(rproc))
		return PTR_ERR(rproc);

If a pointer can be both error and NULL then generally the NULL is a
special kind of success.  It means the option is turned off so there
is nothing to do, so an early return is success.

https://staticthinking.wordpress.com/2022/08/01/mixing-error-pointers-and-null/


102853400321bae Roger Quadros   2023-01-06  343  
102853400321bae Roger Quadros   2023-01-06  344  	if (!rproc->dev.parent || !is_pru_rproc(rproc->dev.parent))
102853400321bae Roger Quadros   2023-01-06  345  		return -ENODEV;
102853400321bae Roger Quadros   2023-01-06  346  
102853400321bae Roger Quadros   2023-01-06  347  	/* pointer is 16 bit and index is 8-bit so mask out the rest */
102853400321bae Roger Quadros   2023-01-06  348  	idx_mask = (c >= PRU_C28) ? 0xFFFF : 0xFF;
102853400321bae Roger Quadros   2023-01-06  349  
102853400321bae Roger Quadros   2023-01-06  350  	/* ctable uses bit 8 and upwards only */
102853400321bae Roger Quadros   2023-01-06  351  	idx = (addr >> 8) & idx_mask;

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