Add ability to generate a drcov trace #7
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andreafioraldi
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Feb 10, 2021
Alexander reported an issue in gic_get_current_cpu() using the
fuzzer. Yet another "deref current_cpu with QTest" bug, reproducible
doing:
$ echo readb 0xf03ff000 | qemu-system-arm -M npcm750-evb,accel=qtest -qtest stdio
[I 1611849440.651452] OPENED
[R +0.242498] readb 0xf03ff000
hw/intc/arm_gic.c:63:29: runtime error: member access within null pointer of type 'CPUState' (aka 'struct CPUState')
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior hw/intc/arm_gic.c:63:29 in
AddressSanitizer:DEADLYSIGNAL
=================================================================
==3719691==ERROR: AddressSanitizer: SEGV on unknown address 0x0000000082a0 (pc 0x5618790ac882 bp 0x7ffca946f4f0 sp 0x7ffca946f4a0 T0)
==3719691==The signal is caused by a READ memory access.
#0 0x5618790ac882 in gic_get_current_cpu hw/intc/arm_gic.c:63:29
#1 0x5618790a8901 in gic_dist_readb hw/intc/arm_gic.c:955:11
#2 0x5618790a7489 in gic_dist_read hw/intc/arm_gic.c:1158:17
#3 0x56187adc573b in memory_region_read_with_attrs_accessor softmmu/memory.c:464:9
#4 0x56187ad7903a in access_with_adjusted_size softmmu/memory.c:552:18
#5 0x56187ad766d6 in memory_region_dispatch_read1 softmmu/memory.c:1426:16
#6 0x56187ad758a8 in memory_region_dispatch_read softmmu/memory.c:1449:9
#7 0x56187b09e84c in flatview_read_continue softmmu/physmem.c:2822:23
#8 0x56187b0a0115 in flatview_read softmmu/physmem.c:2862:12
#9 0x56187b09fc9e in address_space_read_full softmmu/physmem.c:2875:18
#10 0x56187aa88633 in address_space_read include/exec/memory.h:2489:18
#11 0x56187aa88633 in qtest_process_command softmmu/qtest.c:558:13
#12 0x56187aa81881 in qtest_process_inbuf softmmu/qtest.c:797:9
#13 0x56187aa80e02 in qtest_read softmmu/qtest.c:809:5
current_cpu is NULL because QTest accelerator does not use CPU.
Fix by skipping the check and returning the first CPU index when
QTest accelerator is used, similarly to commit c781a2c
("hw/i386/vmport: Allow QTest use without crashing").
Reported-by: Alexander Bulekov <[email protected]>
Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Darren Kenny <[email protected]>
Reviewed-by: Alexander Bulekov <[email protected]>
Message-id: [email protected]
Signed-off-by: Peter Maydell <[email protected]>
andreafioraldi
pushed a commit
that referenced
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Feb 10, 2021
When the reconnect in NBD client is in progress, the iochannel used for
NBD connection doesn't exist. Therefore an attempt to detach it from
the aio_context of the parent BlockDriverState results in a NULL pointer
dereference.
The problem is triggerable, in particular, when an outgoing migration is
about to finish, and stopping the dataplane tries to move the
BlockDriverState from the iothread aio_context to the main loop. If the
NBD connection is lost before this point, and the NBD client has entered
the reconnect procedure, QEMU crashes:
#0 qemu_aio_coroutine_enter (ctx=0x5618056c7580, co=0x0)
at /build/qemu-6MF7tq/qemu-5.0.1/util/qemu-coroutine.c:109
#1 0x00005618034b1b68 in nbd_client_attach_aio_context_bh (
opaque=0x561805ed4c00) at /build/qemu-6MF7tq/qemu-5.0.1/block/nbd.c:164
#2 0x000056180353116b in aio_wait_bh (opaque=0x7f60e1e63700)
at /build/qemu-6MF7tq/qemu-5.0.1/util/aio-wait.c:55
#3 0x0000561803530633 in aio_bh_call (bh=0x7f60d40a7e80)
at /build/qemu-6MF7tq/qemu-5.0.1/util/async.c:136
#4 aio_bh_poll (ctx=ctx@entry=0x5618056c7580)
at /build/qemu-6MF7tq/qemu-5.0.1/util/async.c:164
#5 0x0000561803533e5a in aio_poll (ctx=ctx@entry=0x5618056c7580,
blocking=blocking@entry=true)
at /build/qemu-6MF7tq/qemu-5.0.1/util/aio-posix.c:650
#6 0x000056180353128d in aio_wait_bh_oneshot (ctx=0x5618056c7580,
cb=<optimized out>, opaque=<optimized out>)
at /build/qemu-6MF7tq/qemu-5.0.1/util/aio-wait.c:71
#7 0x000056180345c50a in bdrv_attach_aio_context (new_context=0x5618056c7580,
bs=0x561805ed4c00) at /build/qemu-6MF7tq/qemu-5.0.1/block.c:6172
#8 bdrv_set_aio_context_ignore (bs=bs@entry=0x561805ed4c00,
new_context=new_context@entry=0x5618056c7580,
ignore=ignore@entry=0x7f60e1e63780)
at /build/qemu-6MF7tq/qemu-5.0.1/block.c:6237
#9 0x000056180345c969 in bdrv_child_try_set_aio_context (
bs=bs@entry=0x561805ed4c00, ctx=0x5618056c7580,
ignore_child=<optimized out>, errp=<optimized out>)
at /build/qemu-6MF7tq/qemu-5.0.1/block.c:6332
#10 0x00005618034957db in blk_do_set_aio_context (blk=0x56180695b3f0,
new_context=0x5618056c7580, update_root_node=update_root_node@entry=true,
errp=errp@entry=0x0)
at /build/qemu-6MF7tq/qemu-5.0.1/block/block-backend.c:1989
#11 0x00005618034980bd in blk_set_aio_context (blk=<optimized out>,
new_context=<optimized out>, errp=errp@entry=0x0)
at /build/qemu-6MF7tq/qemu-5.0.1/block/block-backend.c:2010
#12 0x0000561803197953 in virtio_blk_data_plane_stop (vdev=<optimized out>)
at /build/qemu-6MF7tq/qemu-5.0.1/hw/block/dataplane/virtio-blk.c:292
#13 0x00005618033d67bf in virtio_bus_stop_ioeventfd (bus=0x5618056d9f08)
at /build/qemu-6MF7tq/qemu-5.0.1/hw/virtio/virtio-bus.c:245
#14 0x00005618031c9b2e in virtio_vmstate_change (opaque=0x5618056d9f90,
running=0, state=<optimized out>)
at /build/qemu-6MF7tq/qemu-5.0.1/hw/virtio/virtio.c:3220
#15 0x0000561803208bfd in vm_state_notify (running=running@entry=0,
state=state@entry=RUN_STATE_FINISH_MIGRATE)
at /build/qemu-6MF7tq/qemu-5.0.1/softmmu/vl.c:1275
#16 0x0000561803155c02 in do_vm_stop (state=RUN_STATE_FINISH_MIGRATE,
send_stop=<optimized out>) at /build/qemu-6MF7tq/qemu-5.0.1/cpus.c:1032
#17 0x00005618033e3765 in migration_completion (s=0x5618056e6960)
at /build/qemu-6MF7tq/qemu-5.0.1/migration/migration.c:2914
#18 migration_iteration_run (s=0x5618056e6960)
at /build/qemu-6MF7tq/qemu-5.0.1/migration/migration.c:3275
#19 migration_thread (opaque=opaque@entry=0x5618056e6960)
at /build/qemu-6MF7tq/qemu-5.0.1/migration/migration.c:3439
#20 0x0000561803536ad6 in qemu_thread_start (args=<optimized out>)
at /build/qemu-6MF7tq/qemu-5.0.1/util/qemu-thread-posix.c:519
#21 0x00007f61085d06ba in start_thread ()
from /lib/x86_64-linux-gnu/libpthread.so.0
#22 0x00007f610830641d in sysctl () from /lib/x86_64-linux-gnu/libc.so.6
#23 0x0000000000000000 in ?? ()
Fix it by checking that the iochannel is non-null before trying to
detach it from the aio_context. If it is null, no detaching is needed,
and it will get reattached in the proper aio_context once the connection
is reestablished.
Signed-off-by: Roman Kagan <[email protected]>
Reviewed-by: Vladimir Sementsov-Ogievskiy <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Eric Blake <[email protected]>
andreafioraldi
pushed a commit
that referenced
this issue
Feb 10, 2021
When an NBD block driver state is moved from one aio_context to another
(e.g. when doing a drain in a migration thread),
nbd_client_attach_aio_context_bh is executed that enters the connection
coroutine.
However, the assumption that ->connection_co is always present here
appears incorrect: the connection may have encountered an error other
than -EIO in the underlying transport, and thus may have decided to quit
rather than keep trying to reconnect, and therefore it may have
terminated the connection coroutine. As a result an attempt to reassign
the client in this state (NBD_CLIENT_QUIT) to a different aio_context
leads to a null pointer dereference:
#0 qio_channel_detach_aio_context (ioc=0x0)
at /build/qemu-gYtjVn/qemu-5.0.1/io/channel.c:452
#1 0x0000562a242824b3 in bdrv_detach_aio_context (bs=0x562a268d6a00)
at /build/qemu-gYtjVn/qemu-5.0.1/block.c:6151
#2 bdrv_set_aio_context_ignore (bs=bs@entry=0x562a268d6a00,
new_context=new_context@entry=0x562a260c9580,
ignore=ignore@entry=0x7feeadc9b780)
at /build/qemu-gYtjVn/qemu-5.0.1/block.c:6230
#3 0x0000562a24282969 in bdrv_child_try_set_aio_context
(bs=bs@entry=0x562a268d6a00, ctx=0x562a260c9580,
ignore_child=<optimized out>, errp=<optimized out>)
at /build/qemu-gYtjVn/qemu-5.0.1/block.c:6332
#4 0x0000562a242bb7db in blk_do_set_aio_context (blk=0x562a2735d0d0,
new_context=0x562a260c9580,
update_root_node=update_root_node@entry=true, errp=errp@entry=0x0)
at /build/qemu-gYtjVn/qemu-5.0.1/block/block-backend.c:1989
#5 0x0000562a242be0bd in blk_set_aio_context (blk=<optimized out>,
new_context=<optimized out>, errp=errp@entry=0x0)
at /build/qemu-gYtjVn/qemu-5.0.1/block/block-backend.c:2010
#6 0x0000562a23fbd953 in virtio_blk_data_plane_stop (vdev=<optimized
out>)
at /build/qemu-gYtjVn/qemu-5.0.1/hw/block/dataplane/virtio-blk.c:292
#7 0x0000562a241fc7bf in virtio_bus_stop_ioeventfd (bus=0x562a260dbf08)
at /build/qemu-gYtjVn/qemu-5.0.1/hw/virtio/virtio-bus.c:245
#8 0x0000562a23fefb2e in virtio_vmstate_change (opaque=0x562a260dbf90,
running=0, state=<optimized out>)
at /build/qemu-gYtjVn/qemu-5.0.1/hw/virtio/virtio.c:3220
#9 0x0000562a2402ebfd in vm_state_notify (running=running@entry=0,
state=state@entry=RUN_STATE_FINISH_MIGRATE)
at /build/qemu-gYtjVn/qemu-5.0.1/softmmu/vl.c:1275
#10 0x0000562a23f7bc02 in do_vm_stop (state=RUN_STATE_FINISH_MIGRATE,
send_stop=<optimized out>)
at /build/qemu-gYtjVn/qemu-5.0.1/cpus.c:1032
#11 0x0000562a24209765 in migration_completion (s=0x562a260e83a0)
at /build/qemu-gYtjVn/qemu-5.0.1/migration/migration.c:2914
#12 migration_iteration_run (s=0x562a260e83a0)
at /build/qemu-gYtjVn/qemu-5.0.1/migration/migration.c:3275
#13 migration_thread (opaque=opaque@entry=0x562a260e83a0)
at /build/qemu-gYtjVn/qemu-5.0.1/migration/migration.c:3439
#14 0x0000562a2435ca96 in qemu_thread_start (args=<optimized out>)
at /build/qemu-gYtjVn/qemu-5.0.1/util/qemu-thread-posix.c:519
#15 0x00007feed31466ba in start_thread (arg=0x7feeadc9c700)
at pthread_create.c:333
#16 0x00007feed2e7c41d in __GI___sysctl (name=0x0, nlen=608471908,
oldval=0x562a2452b138, oldlenp=0x0, newval=0x562a2452c5e0
<__func__.28102>, newlen=0)
at ../sysdeps/unix/sysv/linux/sysctl.c:30
#17 0x0000000000000000 in ?? ()
Fix it by checking that the connection coroutine is non-null before
trying to enter it. If it is null, no entering is needed, as the
connection is probably going down anyway.
Signed-off-by: Roman Kagan <[email protected]>
Reviewed-by: Vladimir Sementsov-Ogievskiy <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Eric Blake <[email protected]>
andreafioraldi
pushed a commit
that referenced
this issue
Feb 10, 2021
Address space is destroyed without proper removal of its listeners with
current code. They are expected to be removed in
virtio_device_instance_finalize [1], but qemu calls it through
object_deinit, after address_space_destroy call through
device_set_realized [2].
Move it to virtio_device_unrealize, called before device_set_realized
[3] and making it symmetric with memory_listener_register in
virtio_device_realize.
v2: Delete no-op call of virtio_device_instance_finalize.
Add backtraces.
[1]
#0 virtio_device_instance_finalize (obj=0x555557de5120)
at /home/qemu/include/hw/virtio/virtio.h:71
#1 0x0000555555b703c9 in object_deinit (type=0x555556639860,
obj=<optimized out>) at ../qom/object.c:671
#2 object_finalize (data=0x555557de5120) at ../qom/object.c:685
#3 object_unref (objptr=0x555557de5120) at ../qom/object.c:1184
#4 0x0000555555b4de9d in bus_free_bus_child (kid=0x555557df0660)
at ../hw/core/qdev.c:55
#5 0x0000555555c65003 in call_rcu_thread (opaque=opaque@entry=0x0)
at ../util/rcu.c:281
Queued by:
#0 bus_remove_child (bus=0x555557de5098,
child=child@entry=0x555557de5120) at ../hw/core/qdev.c:60
#1 0x0000555555b4ee31 in device_unparent (obj=<optimized out>)
at ../hw/core/qdev.c:984
#2 0x0000555555b70465 in object_finalize_child_property (
obj=<optimized out>, name=<optimized out>, opaque=0x555557de5120)
at ../qom/object.c:1725
#3 0x0000555555b6fa17 in object_property_del_child (
child=0x555557de5120, obj=0x555557ddcf90) at ../qom/object.c:645
#4 object_unparent (obj=0x555557de5120) at ../qom/object.c:664
#5 0x0000555555b4c071 in bus_unparent (obj=<optimized out>)
at ../hw/core/bus.c:147
#6 0x0000555555b70465 in object_finalize_child_property (
obj=<optimized out>, name=<optimized out>, opaque=0x555557de5098)
at ../qom/object.c:1725
#7 0x0000555555b6fa17 in object_property_del_child (
child=0x555557de5098, obj=0x555557ddcf90) at ../qom/object.c:645
#8 object_unparent (obj=0x555557de5098) at ../qom/object.c:664
#9 0x0000555555b4ee19 in device_unparent (obj=<optimized out>)
at ../hw/core/qdev.c:981
#10 0x0000555555b70465 in object_finalize_child_property (
obj=<optimized out>, name=<optimized out>, opaque=0x555557ddcf90)
at ../qom/object.c:1725
#11 0x0000555555b6fa17 in object_property_del_child (
child=0x555557ddcf90, obj=0x55555685da10) at ../qom/object.c:645
#12 object_unparent (obj=0x555557ddcf90) at ../qom/object.c:664
#13 0x00005555558dc331 in pci_for_each_device_under_bus (
opaque=<optimized out>, fn=<optimized out>, bus=<optimized out>)
at ../hw/pci/pci.c:1654
[2]
Optimizer omits pci_qdev_unrealize, called by device_set_realized, and
do_pci_unregister_device, called by pci_qdev_unrealize and caller of
address_space_destroy.
#0 address_space_destroy (as=0x555557ddd1b8)
at ../softmmu/memory.c:2840
#1 0x0000555555b4fc53 in device_set_realized (obj=0x555557ddcf90,
value=<optimized out>, errp=0x7fffeea8f1e0)
at ../hw/core/qdev.c:850
#2 0x0000555555b6eaa6 in property_set_bool (obj=0x555557ddcf90,
v=<optimized out>, name=<optimized out>, opaque=0x555556650ba0,
errp=0x7fffeea8f1e0) at ../qom/object.c:2255
#3 0x0000555555b70e07 in object_property_set (
obj=obj@entry=0x555557ddcf90,
name=name@entry=0x555555db99df "realized",
v=v@entry=0x7fffe46b7500,
errp=errp@entry=0x5555565bbf38 <error_abort>)
at ../qom/object.c:1400
#4 0x0000555555b73c5f in object_property_set_qobject (
obj=obj@entry=0x555557ddcf90,
name=name@entry=0x555555db99df "realized",
value=value@entry=0x7fffe44f6180,
errp=errp@entry=0x5555565bbf38 <error_abort>)
at ../qom/qom-qobject.c:28
#5 0x0000555555b71044 in object_property_set_bool (
obj=0x555557ddcf90, name=0x555555db99df "realized",
value=<optimized out>, errp=0x5555565bbf38 <error_abort>)
at ../qom/object.c:1470
#6 0x0000555555921cb7 in pcie_unplug_device (bus=<optimized out>,
dev=0x555557ddcf90,
opaque=<optimized out>) at /home/qemu/include/hw/qdev-core.h:17
#7 0x00005555558dc331 in pci_for_each_device_under_bus (
opaque=<optimized out>, fn=<optimized out>,
bus=<optimized out>) at ../hw/pci/pci.c:1654
[3]
#0 virtio_device_unrealize (dev=0x555557de5120)
at ../hw/virtio/virtio.c:3680
#1 0x0000555555b4fc63 in device_set_realized (obj=0x555557de5120,
value=<optimized out>, errp=0x7fffee28df90)
at ../hw/core/qdev.c:850
#2 0x0000555555b6eab6 in property_set_bool (obj=0x555557de5120,
v=<optimized out>, name=<optimized out>, opaque=0x555556650ba0,
errp=0x7fffee28df90) at ../qom/object.c:2255
#3 0x0000555555b70e17 in object_property_set (
obj=obj@entry=0x555557de5120,
name=name@entry=0x555555db99ff "realized",
v=v@entry=0x7ffdd8035040,
errp=errp@entry=0x5555565bbf38 <error_abort>)
at ../qom/object.c:1400
#4 0x0000555555b73c6f in object_property_set_qobject (
obj=obj@entry=0x555557de5120,
name=name@entry=0x555555db99ff "realized",
value=value@entry=0x7ffdd8035020,
errp=errp@entry=0x5555565bbf38 <error_abort>)
at ../qom/qom-qobject.c:28
#5 0x0000555555b71054 in object_property_set_bool (
obj=0x555557de5120, name=name@entry=0x555555db99ff "realized",
value=value@entry=false, errp=0x5555565bbf38 <error_abort>)
at ../qom/object.c:1470
#6 0x0000555555b4edc5 in qdev_unrealize (dev=<optimized out>)
at ../hw/core/qdev.c:403
#7 0x0000555555b4c2a9 in bus_set_realized (obj=<optimized out>,
value=<optimized out>, errp=<optimized out>)
at ../hw/core/bus.c:204
#8 0x0000555555b6eab6 in property_set_bool (obj=0x555557de5098,
v=<optimized out>, name=<optimized out>, opaque=0x555557df04c0,
errp=0x7fffee28e0a0) at ../qom/object.c:2255
#9 0x0000555555b70e17 in object_property_set (
obj=obj@entry=0x555557de5098,
name=name@entry=0x555555db99ff "realized",
v=v@entry=0x7ffdd8034f50,
errp=errp@entry=0x5555565bbf38 <error_abort>)
at ../qom/object.c:1400
#10 0x0000555555b73c6f in object_property_set_qobject (
obj=obj@entry=0x555557de5098,
name=name@entry=0x555555db99ff "realized",
value=value@entry=0x7ffdd8020630,
errp=errp@entry=0x5555565bbf38 <error_abort>)
at ../qom/qom-qobject.c:28
#11 0x0000555555b71054 in object_property_set_bool (
obj=obj@entry=0x555557de5098,
name=name@entry=0x555555db99ff "realized",
value=value@entry=false, errp=0x5555565bbf38 <error_abort>)
at ../qom/object.c:1470
#12 0x0000555555b4c725 in qbus_unrealize (
bus=bus@entry=0x555557de5098) at ../hw/core/bus.c:178
#13 0x0000555555b4fc00 in device_set_realized (obj=0x555557ddcf90,
value=<optimized out>, errp=0x7fffee28e1e0)
at ../hw/core/qdev.c:844
#14 0x0000555555b6eab6 in property_set_bool (obj=0x555557ddcf90,
v=<optimized out>, name=<optimized out>, opaque=0x555556650ba0,
errp=0x7fffee28e1e0) at ../qom/object.c:2255
#15 0x0000555555b70e17 in object_property_set (
obj=obj@entry=0x555557ddcf90,
name=name@entry=0x555555db99ff "realized",
v=v@entry=0x7ffdd8020560,
errp=errp@entry=0x5555565bbf38 <error_abort>)
at ../qom/object.c:1400
#16 0x0000555555b73c6f in object_property_set_qobject (
obj=obj@entry=0x555557ddcf90,
name=name@entry=0x555555db99ff "realized",
value=value@entry=0x7ffdd8020540,
errp=errp@entry=0x5555565bbf38 <error_abort>)
at ../qom/qom-qobject.c:28
#17 0x0000555555b71054 in object_property_set_bool (
obj=0x555557ddcf90, name=0x555555db99ff "realized",
value=<optimized out>, errp=0x5555565bbf38 <error_abort>)
at ../qom/object.c:1470
#18 0x0000555555921cb7 in pcie_unplug_device (bus=<optimized out>,
dev=0x555557ddcf90, opaque=<optimized out>)
at /home/qemu/include/hw/qdev-core.h:17
#19 0x00005555558dc331 in pci_for_each_device_under_bus (
opaque=<optimized out>, fn=<optimized out>, bus=<optimized out>)
at ../hw/pci/pci.c:1654
Fixes: c611c76 ("virtio: add MemoryListener to cache ring translations")
Buglink: https://bugs.launchpad.net/qemu/+bug/1912846
Signed-off-by: Eugenio Pérez <[email protected]>
Message-Id: <[email protected]>
Reviewed-by: Peter Xu <[email protected]>
Acked-by: Jason Wang <[email protected]>
Reviewed-by: Stefano Garzarella <[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
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Using the tracing facility would be cool if you can pass something like
AFL_QEMU_DRCOV_TRACE="/tmp/trace.drcov"and qemu will trace the execution with-trace exec_tband, once done, it convert the trace into drcov format like in https://github.com/RobertBuhren/qemutrace2drcov/blob/master/qemutrace2drcov.py that u can drop into lighthouse.What u think?
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