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[MONO][Marshal] Fix race condition in marshal callback installation #77383

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[MONO][Marshal] Fix race condition in marshal callback installation #77383

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80c4635
Added fix for race condition.
Oct 22, 2022
c5ac405
Write barrier/g_free.
Oct 24, 2022
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Write barrier/g_free.
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Nathan Ricci committed Oct 24, 2022
commit c5ac405a0fe510c5bc4077838b480a037be218f0
7 changes: 4 additions & 3 deletions src/mono/mono/metadata/marshal-ilgen.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,13 +35,14 @@ void
mono_install_marshal_callbacks_ilgen (MonoMarshalIlgenCallbacks *cb)
{
g_assert (cb->version == MONO_MARSHAL_CALLBACKS_VERSION);
MonoMarshalIlgenCallbacks* local_cb = (MonoMarshalIlgenCallbacks*)malloc(sizeof(MonoMarshalIlgenCallbacks));
MonoMarshalIlgenCallbacks* local_cb = (MonoMarshalIlgenCallbacks*)g_malloc(sizeof(MonoMarshalIlgenCallbacks));
memcpy (local_cb, cb, sizeof (MonoMarshalIlgenCallbacks));
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@lambdageek lambdageek Oct 24, 2022

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I think we need a memory barrier between the memcpy and the CAS

Suggested change
memcpy (local_cb, cb, sizeof (MonoMarshalIlgenCallbacks));
memcpy (local_cb, cb, sizeof (MonoMarshalIlgenCallbacks));
mono_memory_barrier ();

mono_memory_barrier ();

if (mono_atomic_cas_ptr((void**)&ilgen_marshal_cb, local_cb, NULL ))
if (mono_atomic_cas_ptr((void**)&ilgen_marshal_cb, local_cb, NULL ) != NULL)
{
// cas failed
free(local_cb);
g_free(local_cb);
}
}

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7 changes: 4 additions & 3 deletions src/mono/mono/metadata/marshal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6244,13 +6244,14 @@ void
mono_install_marshal_callbacks (MonoMarshalLightweightCallbacks *cb)
{
g_assert (cb->version == MONO_MARSHAL_CALLBACKS_VERSION);
MonoMarshalLightweightCallbacks* local_cb = (MonoMarshalLightweightCallbacks*)malloc(sizeof(MonoMarshalLightweightCallbacks));
MonoMarshalLightweightCallbacks* local_cb = (MonoMarshalLightweightCallbacks*)g_malloc(sizeof(MonoMarshalLightweightCallbacks));
memcpy (local_cb, cb, sizeof (MonoMarshalLightweightCallbacks));
mono_memory_barrier ();

if (mono_atomic_cas_ptr((void**)&marshal_lightweight_cb, local_cb, NULL))
if (mono_atomic_cas_ptr((void**)&marshal_lightweight_cb, local_cb, NULL) != NULL)
{
// cas failed
free(local_cb);
g_free(local_cb);
}
}

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