Re: [PATCHv3 3/9] bpf: Introduce bpf_copy_to_kernel() to buffer the content from bpf-prog

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

Hi Pingfan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on bpf-next/net]
[also build test WARNING on bpf-next/master bpf/master arm64/for-next/core linus/master v6.15 next-20250529]
[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/Pingfan-Liu/kexec_file-Make-kexec_image_load_default-global-visible/20250529-122124
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git net
patch link:    https://lore.kernel.org/r/20250529041744.16458-4-piliu%40redhat.com
patch subject: [PATCHv3 3/9] bpf: Introduce bpf_copy_to_kernel() to buffer the content from bpf-prog
config: riscv-randconfig-001-20250529 (https://download.01.org/0day-ci/archive/20250529/202505291926.IPUSqCEj-lkp@intel.com/config)
compiler: clang version 21.0.0git (https://github.com/llvm/llvm-project f819f46284f2a79790038e1f6649172789734ae8)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250529/202505291926.IPUSqCEj-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/202505291926.IPUSqCEj-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> kernel/bpf/helpers_carrier.c:74:17: warning: no previous prototype for function 'bpf_mem_range_result_put' [-Wmissing-prototypes]
      74 | __bpf_kfunc int bpf_mem_range_result_put(struct mem_range_result *result)
         |                 ^
   kernel/bpf/helpers_carrier.c:74:13: note: declare 'static' if the function is not intended to be used outside of this translation unit
      74 | __bpf_kfunc int bpf_mem_range_result_put(struct mem_range_result *result)
         |             ^
         |             static 
   kernel/bpf/helpers_carrier.c:88:7: warning: variable 'kmalloc' set but not used [-Wunused-but-set-variable]
      88 |         bool kmalloc;
         |              ^
>> kernel/bpf/helpers_carrier.c:82:17: warning: no previous prototype for function 'bpf_copy_to_kernel' [-Wmissing-prototypes]
      82 | __bpf_kfunc int bpf_copy_to_kernel(const char *name, char *buf, int size)
         |                 ^
   kernel/bpf/helpers_carrier.c:82:13: note: declare 'static' if the function is not intended to be used outside of this translation unit
      82 | __bpf_kfunc int bpf_copy_to_kernel(const char *name, char *buf, int size)
         |             ^
         |             static 
>> kernel/bpf/helpers_carrier.c:165:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
     165 |         if (!find_listener(item->str)) {
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~
   kernel/bpf/helpers_carrier.c:174:9: note: uninitialized use occurs here
     174 |         return ret;
         |                ^~~
   kernel/bpf/helpers_carrier.c:165:2: note: remove the 'if' if its condition is always false
     165 |         if (!find_listener(item->str)) {
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     166 |                 hash_add(str_listeners, &item->node, hash);
         |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     167 |         } else {
         |         ~~~~~~
   kernel/bpf/helpers_carrier.c:149:9: note: initialize the variable 'ret' to silence this warning
     149 |         int ret;
         |                ^
         |                 = 0
   4 warnings generated.


vim +/bpf_mem_range_result_put +74 kernel/bpf/helpers_carrier.c

    73	
  > 74	__bpf_kfunc int bpf_mem_range_result_put(struct mem_range_result *result)
    75	{
    76		return mem_range_result_put(result);
    77	}
    78	
    79	/*
    80	 * Cache the content in @buf into kernel
    81	 */
  > 82	__bpf_kfunc int bpf_copy_to_kernel(const char *name, char *buf, int size)
    83	{
    84		struct mem_range_result *range;
    85		struct mem_cgroup *memcg, *old_memcg;
    86		struct str_listener *item;
    87		resource_handler handler;
    88		bool kmalloc;
    89		char *kbuf;
    90		int id, ret = 0;
    91	
    92		id = srcu_read_lock(&srcu);
    93		item = find_listener(name);
    94		if (!item) {
    95			srcu_read_unlock(&srcu, id);
    96			return -EINVAL;
    97		}
    98		kmalloc = item->kmalloc;
    99		handler = item->handler;
   100		srcu_read_unlock(&srcu, id);
   101		memcg = get_mem_cgroup_from_current();
   102		old_memcg = set_active_memcg(memcg);
   103		range = kmalloc(sizeof(struct mem_range_result), GFP_KERNEL);
   104		if (!range) {
   105			pr_err("fail to allocate mem_range_result\n");
   106			ret = -ENOMEM;
   107			goto err;
   108		}
   109	
   110		kref_init(&range->ref);
   111		if (item->kmalloc)
   112			kbuf = kmalloc(size, GFP_KERNEL | __GFP_ACCOUNT);
   113		else
   114			kbuf = __vmalloc(size, GFP_KERNEL | __GFP_ACCOUNT);
   115		if (!kbuf) {
   116			kfree(range);
   117			ret = -ENOMEM;
   118			goto err;
   119		}
   120		ret = copy_from_kernel_nofault(kbuf, buf, size);
   121		if (unlikely(ret < 0)) {
   122			kfree(range);
   123			if (item->kmalloc)
   124				kfree(kbuf);
   125			else
   126				vfree(kbuf);
   127			ret = -EINVAL;
   128			goto err;
   129		}
   130		range->kmalloc = item->kmalloc;
   131		range->buf = kbuf;
   132		range->buf_sz = size;
   133		range->data_sz = size;
   134		range->memcg = memcg;
   135		mem_cgroup_tryget(memcg);
   136		range->status = 0;
   137		ret = handler(name, range);
   138		mem_range_result_put(range);
   139	err:
   140		set_active_memcg(old_memcg);
   141		mem_cgroup_put(memcg);
   142		return ret;
   143	}
   144	
   145	int register_carrier_listener(struct carrier_listener *listener)
   146	{
   147		struct str_listener *item;
   148		unsigned int hash;
   149		int ret;
   150	
   151		if (!listener->name)
   152			return -EINVAL;
   153		item = kmalloc(sizeof(*item), GFP_KERNEL);
   154		if (!item)
   155			return -ENOMEM;
   156		item->str = kstrdup(listener->name, GFP_KERNEL);
   157		if (!item->str) {
   158			kfree(item);
   159			return -ENOMEM;
   160		}
   161		item->handler = listener->handler;
   162		item->kmalloc = listener->kmalloc;
   163		hash = jhash(item->str, strlen(item->str), 0);
   164		mutex_lock(&str_listeners_mutex);
 > 165		if (!find_listener(item->str)) {
   166			hash_add(str_listeners, &item->node, hash);
   167		} else {
   168			kfree(item->str);
   169			kfree(item);
   170			ret = -EBUSY;
   171		}
   172		mutex_unlock(&str_listeners_mutex);
   173	
   174		return ret;
   175	}
   176	EXPORT_SYMBOL(register_carrier_listener);
   177	

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