[staging:staging-testing 17/17] drivers/staging/vme_user/vme.c:296 vme_slave_request() error: we previously assumed 'slave_image' could be null (see line 297)

Hi Jinjie,

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/gregkh/staging.git staging-testing
head:   4c5ba1d7a93e098aececbf93afbdd7add98ec6f3
commit: 4c5ba1d7a93e098aececbf93afbdd7add98ec6f3 [17/17] staging: vme_user: Use list_for_each_entry() helper
config: x86_64-randconfig-161-20230913 (https://download.01.org/0day-ci/archive/20230914/[email protected]/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20230914/[email protected]/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 <[email protected]>
| Reported-by: Dan Carpenter <[email protected]>
| Closes: https://lore.kernel.org/r/[email protected]/

smatch warnings:
drivers/staging/vme_user/vme.c:296 vme_slave_request() error: we previously assumed 'slave_image' could be null (see line 297)
drivers/staging/vme_user/vme.c:492 vme_master_request() error: we previously assumed 'master_image' could be null (see line 493)
drivers/staging/vme_user/vme.c:866 vme_dma_request() error: we previously assumed 'dma_ctrlr' could be null (see line 867)
drivers/staging/vme_user/vme.c:1460 vme_lm_request() error: we previously assumed 'lm' could be null (see line 1461)

vim +/slave_image +296 drivers/staging/vme_user/vme.c

6af04b065b048e drivers/staging/vme/vme.c      Martyn Welch    2011-12-01  281  struct vme_resource *vme_slave_request(struct vme_dev *vdev, u32 address,
6af04b065b048e drivers/staging/vme/vme.c      Martyn Welch    2011-12-01  282  				       u32 cycle)
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  283  {
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  284  	struct vme_bridge *bridge;
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  285  	struct vme_slave_resource *allocated_image = NULL;
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  286  	struct vme_slave_resource *slave_image = NULL;
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  287  	struct vme_resource *resource = NULL;
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  288  
8f966dc444b11a drivers/staging/vme/vme.c      Manohar Vanga   2011-09-26  289  	bridge = vdev->bridge;
61282c04984e40 drivers/vme/vme.c              Markus Elfring  2017-08-24  290  	if (!bridge) {
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  291  		printk(KERN_ERR "Can't find VME bus\n");
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  292  		goto err_bus;
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  293  	}
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  294  
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  295  	/* Loop through slave resources */
4c5ba1d7a93e09 drivers/staging/vme_user/vme.c Jinjie Ruan     2023-08-23 @296  	list_for_each_entry(slave_image, &bridge->slave_resources, list) {
                                                                                                    ^^^^^^^^^^^
This is the iterator.

61282c04984e40 drivers/vme/vme.c              Markus Elfring  2017-08-24 @297  		if (!slave_image) {

And list iterators are never NULL.  Please remove this if statement.

ead1f3e301e2d8 drivers/staging/vme/vme.c      Martyn Welch    2009-12-15  298  			printk(KERN_ERR "Registered NULL Slave resource\n");
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  299  			continue;
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  300  		}
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  301  
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  302  		/* Find an unlocked and compatible image */
886953e9b70bcb drivers/staging/vme/vme.c      Emilio G. Cota  2010-11-12  303  		mutex_lock(&slave_image->mtx);
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  304  		if (((slave_image->address_attr & address) == address) &&
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  305  		    ((slave_image->cycle_attr & cycle) == cycle) &&
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  306  		    (slave_image->locked == 0)) {
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  307  			slave_image->locked = 1;
886953e9b70bcb drivers/staging/vme/vme.c      Emilio G. Cota  2010-11-12  308  			mutex_unlock(&slave_image->mtx);
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  309  			allocated_image = slave_image;
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  310  			break;
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  311  		}
886953e9b70bcb drivers/staging/vme/vme.c      Emilio G. Cota  2010-11-12  312  		mutex_unlock(&slave_image->mtx);
a17a75e2666f71 drivers/staging/vme/vme.c      Martyn Welch    2009-07-31  313  	}

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