Re: [PATCH] pci: check address before reading configuration bytes

[Daniel P . Berrangé]

On Wed, Jun 03, 2020 at 06:10:41PM +0530, P J P wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
> 
> While reading PCI configuration bytes, a guest may send an
> address towards the end of the configuration space. It may lead
> to an OOB access issue. Add check to ensure 'address + len' is
> within PCI configuration space.

A malicious guest triggering an OOB access in the host QEMU
sounds like a significant security flaw. Do we have a CVE
assigned for this ?

> 
> Reported-by: Ren Ding <rding@gatech.edu>
> Reported-by: Hanqing Zhao <hanqing@gatech.edu>
> Reported-by: Yi Ren <c4tren@gmail.com>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/pci/pci.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index 70c66965f5..4429fa9401 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -1385,7 +1385,9 @@ uint32_t pci_default_read_config(PCIDevice *d,
>          ranges_overlap(address, len, d->exp.exp_cap + PCI_EXP_LNKSTA, 2)) {
>          pcie_sync_bridge_lnk(d);
>      }
> -    memcpy(&val, d->config + address, len);
> +    if (address + len <= pci_config_size(d)) {
> +        memcpy(&val, d->config + address, len);
> +    }
>      return le32_to_cpu(val);
>  }
>  
> -- 
> 2.26.2
> 
> 

Regards,
Daniel
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