[PATCH v2 2/2] pci: ensure configuration access is within bounds

[P J P <ppandit@redhat.com>]

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. Assert that 'address + len' is within
PCI configuration space.

Suggested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/pci/pci.c | 2 ++
 1 file changed, 2 insertions(+)

Update v2: assert PCI configuration access is within bounds
  -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00711.html

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 70c66965f5..173bec4fd5 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -1381,6 +1381,8 @@ uint32_t pci_default_read_config(PCIDevice *d,
 {
     uint32_t val = 0;
 
+    assert(address + len <= pci_config_size(d));
+
     if (pci_is_express_downstream_port(d) &&
         ranges_overlap(address, len, d->exp.exp_cap + PCI_EXP_LNKSTA, 2)) {
         pcie_sync_bridge_lnk(d);
-- 
2.26.2