Re: [PATCH] tracing: Take trace_array reference when opening options file

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

Hi Steven,

kernel test robot noticed the following build warnings:

[auto build test WARNING on trace/for-next]
[also build test WARNING on linus/master v7.3-rc1 next-20260901]
[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/Steven-Rostedt/tracing-Take-trace_array-reference-when-opening-options-file/20260901-163620
base:   https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace for-next
patch link:    https://lore.kernel.org/r/20260901163620.6cbe0ada%40gandalf.local.home
patch subject: [PATCH] tracing: Take trace_array reference when opening options file
config: openrisc-randconfig-r072-20260902 (https://download.01.org/0day-ci/archive/20260902/202609021814.YH14WR0q-lkp@intel.com/config)
compiler: or1k-linux-gcc (GCC) 14.3.0
smatch: v0.5.0-9187-g5189e3fb
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260902/202609021814.YH14WR0q-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/202609021814.YH14WR0q-lkp@intel.com/

All warnings (new ones prefixed by >>):

   kernel/trace/trace.c: In function 'trace_array_options_get':
>> kernel/trace/trace.c:7871:30: warning: comparison of distinct pointer types lacks a cast [-Wcompare-distinct-pointer-types]
    7871 |                 if (tr_index >= &tr->trace_flags_index[0] &&
         |                              ^~
   kernel/trace/trace.c:7872:30: warning: comparison of distinct pointer types lacks a cast [-Wcompare-distinct-pointer-types]
    7872 |                     tr_index < &tr->trace_flags_index[TRACE_FLAGS_MAX_SIZE])
         |                              ^


vim +7871 kernel/trace/trace.c

  7844	
  7845	/*
  7846	 * The tr_index is the address of a trace_array->trace_flags_index[]
  7847	 * element that holds the index of the trace flag. But since the
  7848	 * trace_array reference has not been taken yet, it cannot be referenced
  7849	 * as it could have been freed by a rmdir of the instance the trace_array
  7850	 * represents.
  7851	 *
  7852	 * Search the list of trace_arrays and compare the tr_index to the
  7853	 * address of the entire trace_array trace_flags_index array for each
  7854	 * trace_array in the list. If one is matched, then take the reference
  7855	 * and return it. If not, the trace_array no longer exits.
  7856	 */
  7857	static int trace_array_options_get(void *tr_index)
  7858	{
  7859		struct trace_array *tr;
  7860		int ret;
  7861	
  7862		ret = security_locked_down(LOCKDOWN_TRACEFS);
  7863		if (ret)
  7864			return ret;
  7865	
  7866		if (tracing_disabled)
  7867			return -ENODEV;
  7868	
  7869		guard(mutex)(&trace_types_lock);
  7870		list_for_each_entry(tr, &ftrace_trace_arrays, list) {
> 7871			if (tr_index >= &tr->trace_flags_index[0] &&
  7872			    tr_index < &tr->trace_flags_index[TRACE_FLAGS_MAX_SIZE])
  7873				return __trace_array_get(tr);
  7874		}
  7875		return -ENODEV;
  7876	}
  7877	

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