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[Qemu-devel] [PATCH v2] virtio-blk: drain block before cleanup
From: |
Gioh Kim |
Subject: |
[Qemu-devel] [PATCH v2] virtio-blk: drain block before cleanup |
Date: |
Tue, 13 Jun 2017 12:35:21 +0200 |
Hi,
I'd like to report one use-after-free problem which is found by
AddressSanitizer.
My company provides virtualization server with Qemu-2.7.
If customer commands Disk hot-unplug on Web-based application,
the application sends "device_del" and "drive_del" commands to qemu process via
QMP.
It usually works fine.
But I found a corner case like following.
1. Customer commands Disk hot-unplug via Web-based application.
2. The application sends "device_del" that sometimes takes unpredictable time.
3. There are some inflight IOs
4. Customer does reboot or shutdown the guest OS
4. Qemu process generates segfault.
If a disk is unplugged with "device_del" and "drive_del" commands,
qemu does not generate problem. But if only "device_del" command are finished
and
guest os reboots, qemu generates segfault.
I can reproduce that case easily with following commands
1. generate heavy IO on disk in Guest OS
2. run "device_del" on the qemu monitor
3. run "system_reboot" on the qemu monitor
According to AdressSanitizer, VirtQueue is freed by virtio_cleanup but
dereferenced
by asynchronous request. I think asynchronous requests should be finished
before virtio_cleanup, so I added blk_drain() before virtio_cleanup.
Following is configure options I used to build qemu with AddressSanitizer.
./configure --target-list=x86_64-softmmu --extra-cflags="-fsanitize=address
-fno-omit-frame-pointer" --enable-debug
Following is the report of AddressSanitizer.
------------------------------------- 8<
----------------------------------------
==8801==WARNING: ASan doesn't fully support makecontext/swapcontext functions
and may produce false positives in some cases!
==8801==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top:
0x7ffc984da000; bottom 0x7fa524363000; size: 0x005774177000 (375609847808)
False positive error reports may follow
For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
=================================================================
==8801==ERROR: AddressSanitizer: heap-use-after-free on address 0x7fa5240ab82c
at pc 0x55ccd7bffb76 bp 0x7fa524364590 sp 0x7fa524364580
READ of size 2 at 0x7fa5240ab82c thread T0
#0 0x55ccd7bffb75 in virtqueue_fill
/home/gohkim/work/tools/qemu/hw/virtio/virtio.c:284
#1 0x55ccd7bffe46 in virtqueue_push
/home/gohkim/work/tools/qemu/hw/virtio/virtio.c:308
#2 0x55ccd7b66c74 in virtio_blk_req_complete
/home/gohkim/work/tools/qemu/hw/block/virtio-blk.c:58
#3 0x55ccd7b67154 in virtio_blk_rw_complete
/home/gohkim/work/tools/qemu/hw/block/virtio-blk.c:121
#4 0x55ccd83852b9 in blk_aio_complete block/block-backend.c:923
#5 0x55ccd8385a73 in blk_aio_write_entry block/block-backend.c:984
#6 0x55ccd84c7d68 in coroutine_trampoline util/coroutine-ucontext.c:78
#7 0x7fa5702d45cf (/lib/x86_64-linux-gnu/libc.so.6+0x495cf)
0x7fa5240ab82c is located 44 bytes inside of 131072-byte region
[0x7fa5240ab800,0x7fa5240cb800)
freed by thread T0 here:
#0 0x7fa573f876aa in __interceptor_free
(/usr/lib/x86_64-linux-gnu/libasan.so.2+0x986aa)
#1 0x55ccd7c07fa4 in virtio_cleanup
/home/gohkim/work/tools/qemu/hw/virtio/virtio.c:1678
#2 0x55ccd7b6c585 in virtio_blk_device_unrealize
/home/gohkim/work/tools/qemu/hw/block/virtio-blk.c:948
#3 0x55ccd7c09734 in virtio_device_unrealize
/home/gohkim/work/tools/qemu/hw/virtio/virtio.c:1950
#4 0x55ccd7eb9bb7 in device_set_realized hw/core/qdev.c:964
#5 0x55ccd82c1bef in property_set_bool qom/object.c:1853
#6 0x55ccd82be535 in object_property_set qom/object.c:1087
#7 0x55ccd82c454f in object_property_set_qobject qom/qom-qobject.c:27
#8 0x55ccd82be810 in object_property_set_bool qom/object.c:1156
#9 0x55ccd7ec1395 in bus_set_realized hw/core/bus.c:181
#10 0x55ccd82c1bef in property_set_bool qom/object.c:1853
#11 0x55ccd82be535 in object_property_set qom/object.c:1087
#12 0x55ccd82c454f in object_property_set_qobject qom/qom-qobject.c:27
#13 0x55ccd82be810 in object_property_set_bool qom/object.c:1156
#14 0x55ccd7eb9a8a in device_set_realized hw/core/qdev.c:956
#15 0x55ccd82c1bef in property_set_bool qom/object.c:1853
#16 0x55ccd82be535 in object_property_set qom/object.c:1087
#17 0x55ccd82c454f in object_property_set_qobject qom/qom-qobject.c:27
#18 0x55ccd82be810 in object_property_set_bool qom/object.c:1156
#19 0x55ccd7eba820 in device_unparent hw/core/qdev.c:1099
#20 0x55ccd82bf50b in object_finalize_child_property qom/object.c:1362
#21 0x55ccd82bb3c6 in object_property_del_child qom/object.c:422
#22 0x55ccd82bb601 in object_unparent qom/object.c:441
#23 0x55ccd7e221f1 in acpi_pcihp_eject_slot hw/acpi/pcihp.c:139
#24 0x55ccd7e22301 in acpi_pcihp_update_hotplug_bus hw/acpi/pcihp.c:152
#25 0x55ccd7e22600 in acpi_pcihp_update hw/acpi/pcihp.c:176
#26 0x55ccd7e22628 in acpi_pcihp_reset hw/acpi/pcihp.c:182
#27 0x55ccd7e1fc10 in piix4_reset hw/acpi/piix4.c:363
#28 0x55ccd7da4ebd in qemu_devices_reset
/home/gohkim/work/tools/qemu/vl.c:1713
#29 0x55ccd7c28354 in pc_machine_reset
/home/gohkim/work/tools/qemu/hw/i386/pc.c:2178
previously allocated by thread T0 here:
#0 0x7fa573f87b49 in __interceptor_calloc
(/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98b49)
#1 0x7fa5718575d0 in g_malloc0
(/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x4f5d0)
#2 0x55ccd7b6bfa5 in virtio_blk_device_realize
/home/gohkim/work/tools/qemu/hw/block/virtio-blk.c:910
#3 0x55ccd7c09500 in virtio_device_realize
/home/gohkim/work/tools/qemu/hw/virtio/virtio.c:1927
#4 0x55ccd7eb9690 in device_set_realized hw/core/qdev.c:918
#5 0x55ccd82c1bef in property_set_bool qom/object.c:1853
#6 0x55ccd82be535 in object_property_set qom/object.c:1087
#7 0x55ccd82c454f in object_property_set_qobject qom/qom-qobject.c:27
#8 0x55ccd82be810 in object_property_set_bool qom/object.c:1156
#9 0x55ccd81b1b5c in virtio_blk_pci_realize hw/virtio/virtio-pci.c:1897
#10 0x55ccd81b14df in virtio_pci_realize hw/virtio/virtio-pci.c:1799
#11 0x55ccd805e2c5 in pci_qdev_realize hw/pci/pci.c:1966
#12 0x55ccd81b17db in virtio_pci_dc_realize hw/virtio/virtio-pci.c:1852
#13 0x55ccd7eb9690 in device_set_realized hw/core/qdev.c:918
#14 0x55ccd82c1bef in property_set_bool qom/object.c:1853
#15 0x55ccd82be535 in object_property_set qom/object.c:1087
#16 0x55ccd82c454f in object_property_set_qobject qom/qom-qobject.c:27
#17 0x55ccd82be810 in object_property_set_bool qom/object.c:1156
#18 0x55ccd7d8141e in qdev_device_add
/home/gohkim/work/tools/qemu/qdev-monitor.c:618
#19 0x55ccd7dab462 in device_init_func
/home/gohkim/work/tools/qemu/vl.c:2316
#20 0x55ccd84bd18c in qemu_opts_foreach util/qemu-option.c:1116
#21 0x55ccd7db2bdb in main /home/gohkim/work/tools/qemu/vl.c:4507
#22 0x7fa5702ababf in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x20abf)
SUMMARY: AddressSanitizer: heap-use-after-free
/home/gohkim/work/tools/qemu/hw/virtio/virtio.c:284 virtqueue_fill
Shadow bytes around the buggy address:
0x0ff52480d6b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0ff52480d6c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0ff52480d6d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0ff52480d6e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0ff52480d6f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0ff52480d700: fd fd fd fd fd[fd]fd fd fd fd fd fd fd fd fd fd
0x0ff52480d710: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
0x0ff52480d720: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
0x0ff52480d730: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
0x0ff52480d740: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
0x0ff52480d750: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Heap right redzone: fb
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack partial redzone: f4
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
==8801==ABORTING
[v1]: add braces to fix style error
Signed-off-by: Gioh Kim <address@hidden>
---
hw/block/virtio-blk.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 331d766..75b56ed 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -939,6 +939,9 @@ static void virtio_blk_device_unrealize(DeviceState *dev,
Error **errp)
virtio_blk_data_plane_destroy(s->dataplane);
s->dataplane = NULL;
qemu_del_vm_change_state_handler(s->change);
+ if (blk_bs(s->blk) && bdrv_requests_pending(blk_bs(s->blk))) {
+ blk_drain(s->blk);
+ }
blockdev_mark_auto_del(s->blk);
virtio_cleanup(vdev);
}
--
2.5.0
- [Qemu-devel] [PATCH v2] virtio-blk: drain block before cleanup,
Gioh Kim <=