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[Qemu-devel] [PATCH] xen/pt: Set is_express to avoid out-of-bounds write
From: |
Simon Gaiser |
Subject: |
[Qemu-devel] [PATCH] xen/pt: Set is_express to avoid out-of-bounds write |
Date: |
Sat, 28 Oct 2017 04:53:15 +0200 |
The passed-through device might be an express device. In this case the
old code allocated a too small emulated config space in
pci_config_alloc() since pci_config_size() returned the size for a
non-express device. This leads to an out-of-bound write in
xen_pt_config_reg_init(), which sometimes results in crashes. So set
is_express as already done for KVM in vfio-pci.
Shortened ASan report:
==17512==ERROR: AddressSanitizer: heap-buffer-overflow on address
0x611000041648 at pc 0x55e0fdac51ff bp 0x7ffe4af07410 sp 0x7ffe4af07408
WRITE of size 2 at 0x611000041648 thread T0
#0 0x55e0fdac51fe in memcpy /usr/include/x86_64-linux-gnu/bits/string3.h:53
#1 0x55e0fdac51fe in stw_he_p include/qemu/bswap.h:330
#2 0x55e0fdac51fe in stw_le_p include/qemu/bswap.h:379
#3 0x55e0fdac51fe in pci_set_word include/hw/pci/pci.h:490
#4 0x55e0fdac51fe in xen_pt_config_reg_init hw/xen/xen_pt_config_init.c:1991
#5 0x55e0fdac51fe in xen_pt_config_init hw/xen/xen_pt_config_init.c:2067
#6 0x55e0fdabcf4d in xen_pt_realize hw/xen/xen_pt.c:830
#7 0x55e0fdf59666 in pci_qdev_realize hw/pci/pci.c:2034
#8 0x55e0fdda7d3d in device_set_realized hw/core/qdev.c:914
[...]
0x611000041648 is located 8 bytes to the right of 256-byte region
[0x611000041540,0x611000041640)
allocated by thread T0 here:
#0 0x7ff596a94bb8 in __interceptor_calloc
(/usr/lib/x86_64-linux-gnu/libasan.so.4+0xd9bb8)
#1 0x7ff57da66580 in g_malloc0
(/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x50580)
#2 0x55e0fdda7d3d in device_set_realized hw/core/qdev.c:914
[...]
Signed-off-by: Simon Gaiser <address@hidden>
---
I found this by debugging crashes and I'm not familiar with this code,
so I'm not sure if this has no unintended side effects.
hw/xen/xen_pt.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
index b6d71bb52a..90ffd45e7d 100644
--- a/hw/xen/xen_pt.c
+++ b/hw/xen/xen_pt.c
@@ -946,6 +946,7 @@ static void xen_pci_passthrough_class_init(ObjectClass
*klass, void *data)
k->exit = xen_pt_unregister_device;
k->config_read = xen_pt_pci_read_config;
k->config_write = xen_pt_pci_write_config;
+ k->is_express = 1; /* We might be */
set_bit(DEVICE_CATEGORY_MISC, dc->categories);
dc->desc = "Assign an host PCI device with Xen";
dc->props = xen_pci_passthrough_properties;
--
2.15.0.rc1
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