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pci: check bus pointer before dereference

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fix CVE-2020-25742

patch link: https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg05294.html

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>
This commit is contained in:
Prasad J Pandit 2020-10-14 15:00:20 +08:00 committed by Euler Robot
parent d6857d428f
commit 9daa72fa9d
1 changed files with 50 additions and 0 deletions
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50
pci-check-bus-pointer-before-dereference.patch Normal file
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@ -0,0 +1,50 @@
From e393095e6d1456e2fb22f3cde3a9f0a307152562 Mon Sep 17 00:00:00 2001
From: Prasad J Pandit <pjp@fedoraproject.org>
Date: Wed, 14 Oct 2020 15:00:20 +0800
Subject: [PATCH] pci: check bus pointer before dereference
fix CVE-2020-25742
patch link: https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg05294.html
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;
--
2.23.0