Re: [PATCH] iommu/exynos: fix NULL pointer dereference on device_link_add() failure

[kernel test robot <lkp@intel.com>]

Hi Haotian,

kernel test robot noticed the following build warnings:

[auto build test WARNING on krzk/for-next]
[also build test WARNING on arm-perf/for-next/perf pinctrl-samsung/for-next linus/master v7.3-rc6 next-20261008]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Haotian-Zhang/iommu-exynos-fix-NULL-pointer-dereference-on-device_link_add-failure/20261009-114539
base:   https://git.kernel.org/pub/scm/linux/kernel/git/krzk/linux.git for-next
patch link:    https://lore.kernel.org/r/20261009034539.3073100-1-vulab%40iscas.ac.cn
patch subject: [PATCH] iommu/exynos: fix NULL pointer dereference on device_link_add() failure
config: arm-defconfig (https://download.01.org/0day-ci/archive/20261010/202610100049.FvaUUeCb-lkp@intel.com/config)
compiler: clang version 24.0.0git (https://github.com/llvm/llvm-project 242243a5814307de825db3428662d67b064e2cbc)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261010/202610100049.FvaUUeCb-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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202610100049.FvaUUeCb-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/iommu/exynos-iommu.c:1434:39: warning: variable 'tmp' is uninitialized when used here [-Wuninitialized]
    1434 |         list_for_each_entry_continue_reverse(tmp, &owner->controllers,
         |                                              ^~~
   drivers/iommu/exynos-iommu.c:1406:35: note: initialize the variable 'tmp' to silence this warning
    1406 |         struct sysmmu_drvdata *data, *tmp;
         |                                          ^
         |                                           = NULL
   1 warning generated.


vim +/tmp +1434 drivers/iommu/exynos-iommu.c

  1402	
  1403	static struct iommu_device *exynos_iommu_probe_device(struct device *dev)
  1404	{
  1405		struct exynos_iommu_owner *owner = dev_iommu_priv_get(dev);
  1406		struct sysmmu_drvdata *data, *tmp;
  1407	
  1408		if (!has_sysmmu(dev))
  1409			return ERR_PTR(-ENODEV);
  1410	
  1411		list_for_each_entry(data, &owner->controllers, owner_node) {
  1412			/*
  1413			 * SYSMMU will be runtime activated via device link
  1414			 * (dependency) to its master device, so there are no
  1415			 * direct calls to pm_runtime_get/put in this driver.
  1416			 */
  1417			data->link = device_link_add(dev, data->sysmmu,
  1418						     DL_FLAG_STATELESS |
  1419						     DL_FLAG_PM_RUNTIME);
  1420			if (!data->link) {
  1421				dev_err(dev, "Unable to link %s\n",
  1422					dev_name(data->sysmmu));
  1423				goto err_unlink;
  1424			}
  1425		}
  1426	
  1427		/* There is always at least one entry, see exynos_iommu_of_xlate() */
  1428		data = list_first_entry(&owner->controllers,
  1429					struct sysmmu_drvdata, owner_node);
  1430	
  1431		return &data->iommu;
  1432	
  1433	err_unlink:
> 1434		list_for_each_entry_continue_reverse(tmp, &owner->controllers,
  1435						     owner_node)
  1436			device_link_del(tmp->link);
  1437	
  1438		return ERR_PTR(-ENODEV);
  1439	}
  1440	

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