[linux-next:master 2782/3950] kernel/bpf/helpers.c:1784:17: warning: argument 2 null where non-null expected because argument 3 is nonzero

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

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   7fa4d8dc380fbd81a9d702a855c50690c9c6442c
commit: 6877cd392baecf816c2ba896a9d42874628004a5 [2782/3950] bpf: Enable read/write access to skb metadata through a dynptr
config: sparc-randconfig-r063-20250821 (https://download.01.org/0day-ci/archive/20250821/202508212031.ir9b3B6Q-lkp@intel.com/config)
compiler: sparc-linux-gcc (GCC) 15.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250821/202508212031.ir9b3B6Q-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/202508212031.ir9b3B6Q-lkp@intel.com/

All warnings (new ones prefixed by >>):

   kernel/bpf/helpers.c: In function '____bpf_snprintf':
   kernel/bpf/helpers.c:1069:9: warning: function '____bpf_snprintf' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
    1069 |         err = bstr_printf(str, str_size, fmt, data.bin_args);
         |         ^~~
   In function '__bpf_dynptr_read',
       inlined from 'bpf_dynptr_copy' at kernel/bpf/helpers.c:2910:9:
>> kernel/bpf/helpers.c:1784:17: warning: argument 2 null where non-null expected because argument 3 is nonzero [-Wnonnull]
    1784 |                 memmove(dst, bpf_skb_meta_pointer(src->data, src->offset + offset), len);
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   In file included from include/linux/string.h:65,
                    from include/linux/bitmap.h:13,
                    from include/linux/cpumask.h:12,
                    from arch/sparc/include/asm/smp_32.h:15,
                    from arch/sparc/include/asm/smp.h:7,
                    from arch/sparc/include/asm/switch_to_32.h:5,
                    from arch/sparc/include/asm/switch_to.h:7,
                    from arch/sparc/include/asm/ptrace.h:120,
                    from arch/sparc/include/asm/thread_info_32.h:19,
                    from arch/sparc/include/asm/thread_info.h:7,
                    from include/linux/thread_info.h:60,
                    from include/asm-generic/preempt.h:5,
                    from ./arch/sparc/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:79,
                    from include/linux/alloc_tag.h:11,
                    from include/linux/workqueue.h:9,
                    from include/linux/bpf.h:10,
                    from kernel/bpf/helpers.c:4:
   arch/sparc/include/asm/string.h: In function 'bpf_dynptr_copy':
   arch/sparc/include/asm/string.h:12:7: note: in a call to function 'memmove' declared 'nonnull_if_nonzero'
      12 | void *memmove(void *, const void *, __kernel_size_t);
         |       ^~~~~~~
   In function '__bpf_dynptr_write',
       inlined from 'bpf_dynptr_copy' at kernel/bpf/helpers.c:2913:9:
   kernel/bpf/helpers.c:1845:17: warning: argument 1 null where non-null expected because argument 3 is nonzero [-Wnonnull]
    1845 |                 memmove(bpf_skb_meta_pointer(dst->data, dst->offset + offset), src, len);
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   arch/sparc/include/asm/string.h: In function 'bpf_dynptr_copy':
   arch/sparc/include/asm/string.h:12:7: note: in a call to function 'memmove' declared 'nonnull_if_nonzero'
      12 | void *memmove(void *, const void *, __kernel_size_t);
         |       ^~~~~~~


vim +1784 kernel/bpf/helpers.c

  1754	
  1755	static int __bpf_dynptr_read(void *dst, u32 len, const struct bpf_dynptr_kern *src,
  1756				     u32 offset, u64 flags)
  1757	{
  1758		enum bpf_dynptr_type type;
  1759		int err;
  1760	
  1761		if (!src->data || flags)
  1762			return -EINVAL;
  1763	
  1764		err = bpf_dynptr_check_off_len(src, offset, len);
  1765		if (err)
  1766			return err;
  1767	
  1768		type = bpf_dynptr_get_type(src);
  1769	
  1770		switch (type) {
  1771		case BPF_DYNPTR_TYPE_LOCAL:
  1772		case BPF_DYNPTR_TYPE_RINGBUF:
  1773			/* Source and destination may possibly overlap, hence use memmove to
  1774			 * copy the data. E.g. bpf_dynptr_from_mem may create two dynptr
  1775			 * pointing to overlapping PTR_TO_MAP_VALUE regions.
  1776			 */
  1777			memmove(dst, src->data + src->offset + offset, len);
  1778			return 0;
  1779		case BPF_DYNPTR_TYPE_SKB:
  1780			return __bpf_skb_load_bytes(src->data, src->offset + offset, dst, len);
  1781		case BPF_DYNPTR_TYPE_XDP:
  1782			return __bpf_xdp_load_bytes(src->data, src->offset + offset, dst, len);
  1783		case BPF_DYNPTR_TYPE_SKB_META:
> 1784			memmove(dst, bpf_skb_meta_pointer(src->data, src->offset + offset), len);
  1785			return 0;
  1786		default:
  1787			WARN_ONCE(true, "bpf_dynptr_read: unknown dynptr type %d\n", type);
  1788			return -EFAULT;
  1789		}
  1790	}
  1791	

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