Re: [Qemu-devel] [PATCH v2] scsi: check page count while initialising descriptor rings

[P J P]

  Hello Dmitry,

+-- On Wed, 31 Aug 2016, Dmitry Fleytman wrote --+
| > -    if ((ri->reqRingNumPages > PVSCSI_SETUP_RINGS_MAX_NUM_PAGES)
| > -        || (ri->cmpRingNumPages > PVSCSI_SETUP_RINGS_MAX_NUM_PAGES)) {
| > -        return -1;
| > -    }
| 
| Hello Prasad,
| 
| Why did you decide to move this logic out of pvscsi_ring_init_data()?
| Why not just amend existing “if" as you did in v1 of this patch?

  'ri->reqRingNumPages' and 'ri->cmpRingNumPages' values are also used in 
routine 'pvscsi_dbg_dump_tx_rings_config' before 'pvscsi_ring_init_data' call. 
if they were to have arbitrary values, this loop could run longer leading to 
OOB memory access.

    for (i = 0; i < rc->reqRingNumPages; i++) {                                 
        trace_pvscsi_tx_rings_ppn("Request Ring", rc->reqRingPPNs[i]);          
    }

Moving above logic to 'pvscsi_on_cmd_setup_rings' helps both functions.

Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
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