[PATCH] pci: assert configuration access is within bounds

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

From: Prasad J Pandit <pjp@fedoraproject.org>

While accessing PCI configuration bytes, assert that
'address + len' is within PCI configuration space.

Generally it is within bounds. This is more of a defensive
assert, in case a buggy device was to send 'address' which
may go out of bounds.

Suggested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/pci/pci.c | 4 ++++
 1 file changed, 4 insertions(+)

Update v1: defensive assert as separate patch
  -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00957.html
  -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00960.html

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 70c66965f5..7bf2ae6d92 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);
@@ -1394,6 +1396,8 @@ void pci_default_write_config(PCIDevice *d, uint32_t addr, uint32_t val_in, int
     int i, was_irq_disabled = pci_irq_disabled(d);
     uint32_t val = val_in;
 
+    assert(addr + l <= pci_config_size(d));
+
     for (i = 0; i < l; val >>= 8, ++i) {
         uint8_t wmask = d->wmask[addr + i];
         uint8_t w1cmask = d->w1cmask[addr + i];
-- 
2.26.2