Hi Lorenzo,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/0day-ci/linux/commits/Lorenzo-Bianconi/mvneta-introduce-XDP-multi-buffer-support/20210320-055103
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
compiler: nios2-linux-gcc (GCC) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>


cppcheck warnings: (new ones prefixed by >>)
        ^
   net/core/filter.c:10085:6: note: Variable 'ret' is reassigned a value before the old one has been used.
    ret = -EACCES;
        ^
   net/core/filter.c:10090:6: note: Variable 'ret' is reassigned a value before the old one has been used.
    ret = fprog->len;
        ^
>> net/core/filter.c:4593:30: warning: Uninitialized variable: copy_len [uninitvar]
     memcpy(dst_buff, src_buff, copy_len);
                                ^

vim +4593 net/core/filter.c

  4551	
  4552	static unsigned long bpf_xdp_copy(void *dst_buff, const void *ctx,
  4553					  unsigned long off, unsigned long len)
  4554	{
  4555		struct xdp_buff *xdp = (struct xdp_buff *)ctx;
  4556		struct xdp_shared_info *xdp_sinfo;
  4557		unsigned long base_len;
  4558		const void *src_buff;
  4559	
  4560		if (likely(!xdp->mb)) {
  4561			src_buff = xdp->data;
  4562			memcpy(dst_buff, src_buff + off, len);
  4563	
  4564			return 0;
  4565		}
  4566	
  4567		base_len = xdp->data_end - xdp->data;
  4568		xdp_sinfo = xdp_get_shared_info_from_buff(xdp);
  4569		do {
  4570			unsigned long copy_len;
  4571	
  4572			if (off < base_len) {
  4573				src_buff = xdp->data + off;
  4574				copy_len = min(len, base_len - off);
  4575			} else {
  4576				unsigned long frag_off_total = base_len;
  4577				int i;
  4578	
  4579				for (i = 0; i < xdp_sinfo->nr_frags; i++) {
  4580					skb_frag_t *frag = &xdp_sinfo->frags[i];
  4581					unsigned long frag_len = xdp_get_frag_size(frag);
  4582					unsigned long frag_off = off - frag_off_total;
  4583	
  4584					if (frag_off < frag_len) {
  4585						src_buff = xdp_get_frag_address(frag) +
  4586							   frag_off;
  4587						copy_len = min(len, frag_len - frag_off);
  4588						break;
  4589					}
  4590					frag_off_total += frag_len;
  4591				}
  4592			}
> 4593			memcpy(dst_buff, src_buff, copy_len);
  4594			off += copy_len;
  4595			len -= copy_len;
  4596			dst_buff += copy_len;
  4597		} while (len);
  4598	
  4599		return 0;
  4600	}
  4601	

---
0-DAY CI Kernel Test Service, Intel Corporation
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