drivers/dma-buf/dma-fence.c:1112:51: sparse: sparse: incorrect type in return expression (different address spaces)

drivers/dma-buf/dma-fence.c:1112:51: sparse: sparse: incorrect type in return expression (different address spaces)

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   983d014aafb14ee5e4915465bf8948e8f3a723b5
commit: 506aa8b02a8d6898c64cc095d233fbae1cef8b8a dma-fence: Add safe access helpers and document the rules
date:   7 months ago
config: i386-randconfig-063-20260116 (https://download.01.org/0day-ci/archive/20260117/202601170112.FVBMyjX0-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260117/202601170112.FVBMyjX0-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/202601170112.FVBMyjX0-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> drivers/dma-buf/dma-fence.c:1112:51: sparse: sparse: incorrect type in return expression (different address spaces) @@     expected char const [noderef] __rcu * @@     got char const * @@
   drivers/dma-buf/dma-fence.c:1112:51: sparse:     expected char const [noderef] __rcu *
   drivers/dma-buf/dma-fence.c:1112:51: sparse:     got char const *
   drivers/dma-buf/dma-fence.c:1114:24: sparse: sparse: incorrect type in return expression (different address spaces) @@     expected char const [noderef] __rcu * @@     got char * @@
   drivers/dma-buf/dma-fence.c:1114:24: sparse:     expected char const [noderef] __rcu *
   drivers/dma-buf/dma-fence.c:1114:24: sparse:     got char *
   drivers/dma-buf/dma-fence.c:1144:51: sparse: sparse: incorrect type in return expression (different address spaces) @@     expected char const [noderef] __rcu * @@     got char const * @@
   drivers/dma-buf/dma-fence.c:1144:51: sparse:     expected char const [noderef] __rcu *
   drivers/dma-buf/dma-fence.c:1144:51: sparse:     got char const *
   drivers/dma-buf/dma-fence.c:1146:24: sparse: sparse: incorrect type in return expression (different address spaces) @@     expected char const [noderef] __rcu * @@     got char * @@
   drivers/dma-buf/dma-fence.c:1146:24: sparse:     expected char const [noderef] __rcu *
   drivers/dma-buf/dma-fence.c:1146:24: sparse:     got char *
   drivers/dma-buf/dma-fence.c: note: in included file (through include/trace/trace_events.h, include/trace/define_trace.h, include/trace/events/dma_fence.h):
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *str @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected char const *str
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *str @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected char const *str
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *str @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected char const *str
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in assignment (different address spaces) @@     expected void const *driver_ptr_ @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected void const *driver_ptr_
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *str @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected char const *str
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *str @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected char const *str
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *str @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected char const *str
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in assignment (different address spaces) @@     expected void const *timeline_ptr_ @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected void const *timeline_ptr_
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *str @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected char const *str
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *str @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected char const *str
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *str @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected char const *str
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in assignment (different address spaces) @@     expected void const *driver_ptr_ @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected void const *driver_ptr_
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *str @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected char const *str
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *str @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected char const *str
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *str @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected char const *str
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *
   include/trace/events/dma_fence.h:12:1: sparse: sparse: incorrect type in assignment (different address spaces) @@     expected void const *timeline_ptr_ @@     got char const [noderef] __rcu * @@
   include/trace/events/dma_fence.h:12:1: sparse:     expected void const *timeline_ptr_
   include/trace/events/dma_fence.h:12:1: sparse:     got char const [noderef] __rcu *

vim +1112 drivers/dma-buf/dma-fence.c

  1085	
  1086	/**
  1087	 * dma_fence_driver_name - Access the driver name
  1088	 * @fence: the fence to query
  1089	 *
  1090	 * Returns a driver name backing the dma-fence implementation.
  1091	 *
  1092	 * IMPORTANT CONSIDERATION:
  1093	 * Dma-fence contract stipulates that access to driver provided data (data not
  1094	 * directly embedded into the object itself), such as the &dma_fence.lock and
  1095	 * memory potentially accessed by the &dma_fence.ops functions, is forbidden
  1096	 * after the fence has been signalled. Drivers are allowed to free that data,
  1097	 * and some do.
  1098	 *
  1099	 * To allow safe access drivers are mandated to guarantee a RCU grace period
  1100	 * between signalling the fence and freeing said data.
  1101	 *
  1102	 * As such access to the driver name is only valid inside a RCU locked section.
  1103	 * The pointer MUST be both queried and USED ONLY WITHIN a SINGLE block guarded
  1104	 * by the &rcu_read_lock and &rcu_read_unlock pair.
  1105	 */
  1106	const char __rcu *dma_fence_driver_name(struct dma_fence *fence)
  1107	{
  1108		RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
  1109				 "RCU protection is required for safe access to returned string");
  1110	
  1111		if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
> 1112			return fence->ops->get_driver_name(fence);
  1113		else
  1114			return "detached-driver";
  1115	}
  1116	EXPORT_SYMBOL(dma_fence_driver_name);
  1117	

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