Re: [PATCH] pci: check bus pointer before dereference

[P J P]

+-- On Thu, 27 Aug 2020, P J P wrote --+
| While mapping IRQ level in pci_change_irq_level() routine,
| it does not check if pci_get_bus() returned a valid pointer.
| It may lead to a NULL pointer dereference issue. Add check to
| avoid it.
| 
|  -> https://ruhr-uni-bochum.sciebo.de/s/NNWP2GfwzYKeKwE?path=%2Flsi_nullptr1
|     ==1183858==Hint: address points to the zero page.
|     #0 pci_change_irq_level hw/pci/pci.c:259
|     #1 pci_irq_handler hw/pci/pci.c:1445
|     #2 pci_set_irq hw/pci/pci.c:1463
|     #3 lsi_set_irq hw/scsi/lsi53c895a.c:488
|     #4 lsi_update_irq hw/scsi/lsi53c895a.c:523
|     #5 lsi_script_scsi_interrupt hw/scsi/lsi53c895a.c:554
|     #6 lsi_execute_script hw/scsi/lsi53c895a.c:1149
|     #7 lsi_reg_writeb hw/scsi/lsi53c895a.c:1984
|     #8 lsi_io_write hw/scsi/lsi53c895a.c:2146
|     ...
| 
| Reported-by: Ruhr-University <bugs-syssec@rub.de>
| Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
| ---
|  hw/pci/pci.c | 3 +++
|  1 file changed, 3 insertions(+)
| 
| diff --git a/hw/pci/pci.c b/hw/pci/pci.c
| index de0fae10ab..df5a2c3294 100644
| --- a/hw/pci/pci.c
| +++ b/hw/pci/pci.c
| @@ -253,6 +253,9 @@ static void pci_change_irq_level(PCIDevice *pci_dev, int 
irq_num, int change)
|      PCIBus *bus;
|      for (;;) {
|          bus = pci_get_bus(pci_dev);
| +        if (!bus) {
| +            return;
| +        }
|          irq_num = bus->map_irq(pci_dev, irq_num);
|          if (bus->set_irq)
|              break;
| 


Ping...!
--
Prasad J Pandit / Red Hat Product Security Team
8685 545E B54C 486B C6EB 271E E285 8B5A F050 DE8D