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

[Andrea Parri <parri.andrea@gmail.com>]

Hi Dan,

On Wed, Feb 03, 2021 at 01:10:41PM +0300, Dan Carpenter wrote:
> 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().

Right, I did realize about the error and I'm about to send a fix for it.

Thank you for the report,

  Andrea