PVS-Studio warning V579 for OpenSSL

unsigned char cleanse_ctr = 0;

void OPENSSL_cleanse(void *ptr, size_t len)
{
  unsigned char *p = ptr;
  size_t loop = len, ctr = cleanse_ctr;
  while(loop--)
  {
    *(p++) = (unsigned char)ctr;
    ctr += (17 + ((size_t)p & 0xF));
  }
  p=memchr(ptr, (unsigned char)ctr, len);
  if(p)
    ctr += (63 + (size_t)p);
  cleanse_ctr = (unsigned char)ctr;
}

void usage(void)
{
  static unsigned char *buf=NULL,*obuf=NULL;
  ....
problems:
  OPENSSL_cleanse(buf,sizeof(buf));
  OPENSSL_cleanse(obuf,sizeof(obuf));
  ....
}

This suspicious code was found in OpenSSL project by PVS-Studio static code analyzer.
Warning message is:
V579 The OPENSSL_cleanse function receives the pointer and its size as arguments. It is possibly a mistake. Inspect the second argument. des.c 669

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