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4 Commits

Author SHA1 Message Date
Ján Tomko
cc622d25e6 util: do not unref event thread after joining it 
g_thread_join() eats a reference.

==295055== Invalid read of size 4
==295055==    at 0x4DA4AE4: g_thread_unref (in /usr/lib64/libglib-2.0.so.0.6400.5)
==295055==    by 0x491D5FA: vir_event_thread_finalize (vireventthread.c:47)
==295055==    by 0x4E6BCFF: g_object_unref (in /usr/lib64/libgobject-2.0.so.0.6400.5)
==295055==    by 0x22F35CF4: qemuProcessQMPFree (qemu_process.c:8525)
==295055==    by 0x22E71B58: glib_autoptr_clear_qemuProcessQMP (qemu_process.h:237)
...
==295055==    by 0x22E98A29: qemuDomainPostParseDataAlloc (qemu_domain.c:5476)
==295055==    by 0x49ABF83: virDomainDefPostParse (domain_conf.c:6023)
==295055==  Address 0x2acb1c68 is 24 bytes inside a block of size 88 free'd
==295055==    at 0x483B9F5: free (vg_replace_malloc.c:538)
==295055==    by 0x4D80A4C: g_free (in /usr/lib64/libglib-2.0.so.0.6400.5)
...
==295055==    by 0x491D5F1: vir_event_thread_finalize (vireventthread.c:46)
==295055==    by 0x4E6BCFF: g_object_unref (in /usr/lib64/libgobject-2.0.so.0.6400.5)
==295055==    by 0x22F35CF4: qemuProcessQMPFree (qemu_process.c:8525)
==295055==    by 0x22E71B58: glib_autoptr_clear_qemuProcessQMP (qemu_process.h:237)
...
==295055==  Block was alloc'd at
==295055==    at 0x483A809: malloc (vg_replace_malloc.c:307)
==295055==    by 0x4D80958: g_malloc (in /usr/lib64/libglib-2.0.so.0.6400.5)
...
==295055==    by 0x4DA4C32: g_thread_try_new (in /usr/lib64/libglib-2.0.so.0.6400.5)
==295055==    by 0x491D3BC: virEventThreadStart (vireventthread.c:159)
==295055==    by 0x491D3BC: virEventThreadNew (vireventthread.c:185)
...

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Fixes: f4fc3db920
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
 2020-09-23 17:06:36 +02:00
Nikolay Shirokovskiy
f4fc3db920 vireventthread: exit thread synchronously on finalize 
It it useful to be sure no thread is running after we drop all references to
virEventThread. Otherwise in order to avoid crashes we need to synchronize some
other way or we make extra references in event handler callbacks to all the
object in use. And some of them are not prepared to be refcounted.

Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
 2020-09-07 09:33:59 +03:00
Daniel P. Berrangé
2998ba2012 util: avoid race in releasing the GSource in event thread 
There is a race between  vir_event_thread_finalize and
virEventThreadWorker in releasing the last reference on
the GMainContext. If virEventThreadDataFree() runs after
vir_event_thread_finalize releases its reference, then
it will release the last reference on the GMainContext.
As a result g_autoptr cleanup on the GSource will access
free'd memory.

The race can be seen in non-deterministic crashes of the
virt-run-qemu program during its shutdown, but could
also likely affect the main libvirtd QEMU driver:

  Thread 2 (Thread 0x7f508ffff700 (LWP 222813)):
  #0  0x00007f509c8e26b0 in malloc_consolidate (av=av@entry=0x7f5088000020) at malloc.c:4488
  #1  0x00007f509c8e4b08 in _int_malloc (av=av@entry=0x7f5088000020, bytes=bytes@entry=2048) at malloc.c:3711
  #2  0x00007f509c8e6412 in __GI___libc_malloc (bytes=2048) at malloc.c:3073
  #3  0x00007f509d6e925e in g_realloc (mem=0x0, n_bytes=2048) at gmem.c:164
  #4  0x00007f509d705a57 in g_string_maybe_expand (string=string@entry=0x7f5088001f20, len=len@entry=1024) at gstring.c:102
  #5  0x00007f509d705ab6 in g_string_sized_new (dfl_size=dfl_size@entry=1024) at gstring.c:127
  #6  0x00007f509d708c5e in g_test_log_dump (len=<synthetic pointer>, msg=<synthetic pointer>) at gtestutils.c:3330
  #7  0x00007f509d708c5e in g_test_log
      (lbit=G_TEST_LOG_ERROR, string1=0x7f508800fcb0 "GLib:ERROR:ghash.c:377:g_hash_table_lookup_node: assertion failed: (hash_table->ref_count > 0)", string2=<optimized out>, n_args=0, largs=0x0) at gtestutils.c:975
  #8  0x00007f509d70af2a in g_assertion_message
      (domain=<optimized out>, file=0x7f509d7324a2 "ghash.c", line=<optimized out>, func=0x7f509d732750 <__func__.11348> "g_hash_table_lookup_node", message=<optimized out>)
      at gtestutils.c:2504
  #9  0x00007f509d70af8e in g_assertion_message_expr
      (domain=domain@entry=0x7f509d72d76e "GLib", file=file@entry=0x7f509d7324a2 "ghash.c", line=line@entry=377, func=func@entry=0x7f509d732750 <__func__.11348> "g_hash_table_lookup_node", expr=expr@entry=0x7f509d732488 "hash_table->ref_count > 0") at gtestutils.c:2555
  #10 0x00007f509d6d197e in g_hash_table_lookup_node (hash_table=0x55b70ace1760, key=<optimized out>, hash_return=<synthetic pointer>) at ghash.c:377
  #11 0x00007f509d6d197e in g_hash_table_lookup_node (hash_return=<synthetic pointer>, key=<optimized out>, hash_table=0x55b70ace1760) at ghash.c:361
  #12 0x00007f509d6d197e in g_hash_table_remove_internal (hash_table=0x55b70ace1760, key=<optimized out>, notify=1) at ghash.c:1371
  #13 0x00007f509d6e0664 in g_source_unref_internal (source=0x7f5088000b60, context=0x55b70ad87e00, have_lock=0) at gmain.c:2103
  #14 0x00007f509d6e1f64 in g_source_unref (source=<optimized out>) at gmain.c:2176
  #15 0x00007f50a08ff84c in glib_autoptr_cleanup_GSource (_ptr=<synthetic pointer>) at /usr/include/glib-2.0/glib/glib-autocleanups.h:58
  #16 0x00007f50a08ff84c in virEventThreadWorker (opaque=0x55b70ad87f80) at ../../src/util/vireventthread.c:114
  #17 0x00007f509d70bd4a in g_thread_proxy (data=0x55b70acf3850) at gthread.c:784
  #18 0x00007f509d04714a in start_thread (arg=<optimized out>) at pthread_create.c:479
  #19 0x00007f509c95cf23 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

  Thread 1 (Thread 0x7f50a1380c00 (LWP 222802)):
  #0  0x00007f509c8977ff in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
  #1  0x00007f509c881c35 in __GI_abort () at abort.c:79
  #2  0x00007f509d72a823 in g_mutex_clear (mutex=0x55b70ad87e00) at gthread-posix.c:1307
  #3  0x00007f509d72a823 in g_mutex_clear (mutex=mutex@entry=0x55b70ad87e00) at gthread-posix.c:1302
  #4  0x00007f509d6e1a84 in g_main_context_unref (context=0x55b70ad87e00) at gmain.c:582
  #5  0x00007f509d6e1a84 in g_main_context_unref (context=0x55b70ad87e00) at gmain.c:541
  #6  0x00007f50a08ffabb in vir_event_thread_finalize (object=0x55b70ad83180 [virEventThread]) at ../../src/util/vireventthread.c:50
  #7  0x00007f509d9c48a9 in g_object_unref (_object=<optimized out>) at gobject.c:3340
  #8  0x00007f509d9c48a9 in g_object_unref (_object=0x55b70ad83180) at gobject.c:3232

  #9  0x00007f509583d311 in qemuProcessQMPFree (proc=proc@entry=0x55b70ad87b90) at ../../src/qemu/qemu_process.c:8355
  #10 0x00007f5095790f58 in virQEMUCapsInitQMPSingle
      (qemuCaps=qemuCaps@entry=0x55b70ad88010, libDir=libDir@entry=0x55b70ad049e0 "/tmp/virt-qemu-run-VZC9N0/lib/qemu", runUid=runUid@entry=107, runGid=runGid@entry=107, onlyTCG=onlyTCG@entry=false) at ../../src/qemu/qemu_capabilities.c:5409
  #11 0x00007f509579108f in virQEMUCapsInitQMP (runGid=107, runUid=107, libDir=0x55b70ad049e0 "/tmp/virt-qemu-run-VZC9N0/lib/qemu", qemuCaps=0x55b70ad88010)
      at ../../src/qemu/qemu_capabilities.c:5420
  #12 0x00007f509579108f in virQEMUCapsNewForBinaryInternal
      (hostArch=VIR_ARCH_X86_64, binary=binary@entry=0x55b70ad7dc40 "/usr/libexec/qemu-kvm", libDir=0x55b70ad049e0 "/tmp/virt-qemu-run-VZC9N0/lib/qemu", runUid=107, runGid=107, hostCPUSignature=0x55b70ad01320 "GenuineIntel, Intel(R) Xeon(R) Silver 4210 CPU @ 2.20GHz, family: 6, model: 85, stepping: 7", microcodeVersion=83898113, kernelVersion=0x55b70ad00d60 "4.18.0-211.el8.x86_64 #1 SMP Thu Jun 4 08:08:16 UTC 2020") at ../../src/qemu/qemu_capabilities.c:5472
  #13 0x00007f5095791373 in virQEMUCapsNewData (binary=0x55b70ad7dc40 "/usr/libexec/qemu-kvm", privData=0x55b70ad5b8f0) at ../../src/qemu/qemu_capabilities.c:5505
  #14 0x00007f50a09a32b1 in virFileCacheNewData (name=0x55b70ad7dc40 "/usr/libexec/qemu-kvm", cache=<optimized out>) at ../../src/util/virfilecache.c:208
  #15 0x00007f50a09a32b1 in virFileCacheValidate (cache=cache@entry=0x55b70ad5c030, name=name@entry=0x55b70ad7dc40 "/usr/libexec/qemu-kvm", data=data@entry=0x7ffca39ffd90)
      at ../../src/util/virfilecache.c:277
  #16 0x00007f50a09a37ea in virFileCacheLookup (cache=cache@entry=0x55b70ad5c030, name=name@entry=0x55b70ad7dc40 "/usr/libexec/qemu-kvm") at ../../src/util/virfilecache.c:310
  #17 0x00007f5095791627 in virQEMUCapsCacheLookup (cache=0x55b70ad5c030, binary=0x55b70ad7dc40 "/usr/libexec/qemu-kvm") at ../../src/qemu/qemu_capabilities.c:5647
  #18 0x00007f50957c34c3 in qemuDomainPostParseDataAlloc (def=<optimized out>, parseFlags=<optimized out>, opaque=<optimized out>, parseOpaque=0x7ffca39ffe18)
      at ../../src/qemu/qemu_domain.c:5470
  #19 0x00007f50a0a34051 in virDomainDefPostParse
      (def=def@entry=0x55b70ad7d200, parseFlags=parseFlags@entry=258, xmlopt=xmlopt@entry=0x55b70ad5d010, parseOpaque=parseOpaque@entry=0x0)
      at ../../src/conf/domain_conf.c:5970
  #20 0x00007f50a0a464bb in virDomainDefParseNode
      (xml=xml@entry=0x55b70aced140, root=root@entry=0x55b70ad5f020, xmlopt=xmlopt@entry=0x55b70ad5d010, parseOpaque=parseOpaque@entry=0x0, flags=flags@entry=258)
      at ../../src/conf/domain_conf.c:22520
  #21 0x00007f50a0a4669b in virDomainDefParse
      (xmlStr=xmlStr@entry=0x55b70ad5f9e0 "<domain type='kvm'>\n  <name>83</name>\n  <uuid>9350639d-1c8a-4f51-a4a6-4eaf8eabe83e</uuid>\n  <metadata>\n    <libosinfo:libosinfo xmlns:libosinfo=\"http://libosinfo.org/xmlns/libvirt/domain/1.0\">\n      <"..., filename=filename@entry=0x0, xmlopt=0x55b70ad5d010, parseOpaque=parseOpaque@entry=0x0, flags=flags@entry=258) at ../../src/conf/domain_conf.c:22474
  #22 0x00007f50a0a467ae in virDomainDefParseString
      (xmlStr=xmlStr@entry=0x55b70ad5f9e0 "<domain type='kvm'>\n  <name>83</name>\n  <uuid>9350639d-1c8a-4f51-a4a6-4eaf8eabe83e</uuid>\n  <metadata>\n    <libosinfo:libosinfo xmlns:libosinfo=\"http://libosinfo.org/xmlns/libvirt/domain/1.0\">\n      <"..., xmlopt=<optimized out>, parseOpaque=parseOpaque@entry=0x0, flags=flags@entry=258)
      at ../../src/conf/domain_conf.c:22488
  #23 0x00007f50958ce112 in qemuDomainCreateXML
      (conn=0x55b70acf9090, xml=0x55b70ad5f9e0 "<domain type='kvm'>\n  <name>83</name>\n  <uuid>9350639d-1c8a-4f51-a4a6-4eaf8eabe83e</uuid>\n  <metadata>\n    <libosinfo:libosinfo xmlns:libosinfo=\"http://libosinfo.org/xmlns/libvirt/domain/1.0\">\n      <"..., flags=0) at ../../src/qemu/qemu_driver.c:1744
  #24 0x00007f50a0c268ac in virDomainCreateXML
      (conn=0x55b70acf9090, xmlDesc=0x55b70ad5f9e0 "<domain type='kvm'>\n  <name>83</name>\n  <uuid>9350639d-1c8a-4f51-a4a6-4eaf8eabe83e</uuid>\n  <metadata>\n    <libosinfo:libosinfo xmlns:libosinfo=\"http://libosinfo.org/xmlns/libvirt/domain/1.0\">\n      <"..., flags=0) at ../../src/libvirt-domain.c:176
  #25 0x000055b709547e7b in main (argc=<optimized out>, argv=<optimized out>) at ../../src/qemu/qemu_shim.c:289

The solution is to explicitly unref the GSource at a safe time instead
of letting g_autoptr unref it when leaving scope.

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
 2020-08-07 12:44:05 +01:00
Daniel P. Berrangé
5c146f6e57 src: introduce an abstraction for running event loops 
We want a way to easily run a private GMainContext in a
thread, with correct synchronization between startup
and shutdown of the thread.

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
 2020-03-11 14:44:04 +00:00