[bug report] hv_netvsc: Copy packets sent by Hyper-V out of the receive buffer

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Andrea Parri (Microsoft),

This is a semi-automatic email about new static checker warnings.

The patch 0ba35fe91ce3: "hv_netvsc: Copy packets sent by Hyper-V out
of the receive buffer" from Jan 26, 2021, leads to the following
Smatch complaint:

    drivers/net/hyperv/rndis_filter.c:468 rsc_add_data()
    error: we previously assumed 'csum_info' could be null (see line 460)

drivers/net/hyperv/rndis_filter.c
   459			}
   460			if (csum_info != NULL) {
                            ^^^^^^^^^^^^^^^^^
"csum_info" can be NULL.

   461				memcpy(&nvchan->rsc.csum_info, csum_info, sizeof(*csum_info));
   462				nvchan->rsc.ppi_flags |= NVSC_RSC_CSUM_INFO;
   463			} else {
   464				nvchan->rsc.ppi_flags &= ~NVSC_RSC_CSUM_INFO;
   465			}
   466			nvchan->rsc.pktlen = len;
   467			if (hash_info != NULL) {
   468				nvchan->rsc.csum_info = *csum_info;
                                                        ^^^^^^^^^^^
Unchecked dereference.  Plus this has "csum_info" on both sides of the
assignment so maybe it is a copy and paste error?  This is equivalent to
the "memcpy(&nvchan->rsc.csum_info, csum_info, sizeof(*csum_info));"
in the ealier if statement but stated as an assignment instead of a
memcpy().

   469				nvchan->rsc.ppi_flags |= NVSC_RSC_HASH_INFO;
   470			} else {

regards,
dan carpenter