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gsignal: Avoid possible race in g_signal_emit_by_name

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Since we're locking and unlocking once we've found the signal ID, we
might have performed calls to g_signal_emit_valist() with a signal id
that was already been removed, and thus failing later.

This is not really an issue as inside g_signal_emit_valist() we were
re-checking for the signal id, but we can make this more reliable so
that the first thread that acquires the lock can also be sure to emit.
This commit is contained in:
Marco Trevisan (Treviño) 2022-07-15 16:46:38 +02:00 committed by Philip Withnall
parent 0bc725d4fe
commit 2368187eb9
1 changed files with 44 additions and 18 deletions
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62
gobject/gsignal.c
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@ -3312,6 +3312,12 @@ accumulate (GSignalInvocationHint *ihint,
return continue_emission;
}
static gboolean
signal_emit_valist_unlocked (gpointer instance,
guint signal_id,
GQuark detail,
va_list var_args);
/**
* g_signal_emit_valist: (skip)
* @instance: (type GObject.TypeInstance): the instance the signal is being
@ -3333,6 +3339,26 @@ g_signal_emit_valist (gpointer instance,
guint signal_id,
GQuark detail,
va_list var_args)
{
SIGNAL_LOCK ();
if (signal_emit_valist_unlocked (instance, signal_id, detail, var_args))
SIGNAL_UNLOCK ();
}
/*<private>
* signal_emit_valist_unlocked:
* @instance: The instance to emit from
* @signal_id: Signal id to emit
* @detail: Signal detail
* @var_args: Call arguments
*
* Returns: %TRUE if the signal mutex has been left locked
*/
static gboolean
signal_emit_valist_unlocked (gpointer instance,
guint signal_id,
GQuark detail,
va_list var_args)
{
GValue *instance_and_params;
GType signal_return_type;
@ -3340,23 +3366,20 @@ g_signal_emit_valist (gpointer instance,
SignalNode *node;
guint i, n_params;
g_return_if_fail (G_TYPE_CHECK_INSTANCE (instance));
g_return_if_fail (signal_id > 0);
g_return_val_if_fail (G_TYPE_CHECK_INSTANCE (instance), TRUE);
g_return_val_if_fail (signal_id > 0, TRUE);
SIGNAL_LOCK ();
node = LOOKUP_SIGNAL_NODE (signal_id);
if (!node || !g_type_is_a (G_TYPE_FROM_INSTANCE (instance), node->itype))
{
g_critical ("%s: signal id '%u' is invalid for instance '%p'", G_STRLOC, signal_id, instance);
SIGNAL_UNLOCK ();
return;
return TRUE;
}
#ifndef G_DISABLE_CHECKS
if (detail && !(node->flags & G_SIGNAL_DETAILED))
{
g_critical ("%s: signal id '%u' does not support detail (%u)", G_STRLOC, signal_id, detail);
SIGNAL_UNLOCK ();
return;
return TRUE;
}
#endif /* !G_DISABLE_CHECKS */
@ -3416,10 +3439,7 @@ g_signal_emit_valist (gpointer instance,
}
if (fastpath && closure == NULL && node->return_type == G_TYPE_NONE)
{
SIGNAL_UNLOCK ();
return;
}
return TRUE;
/* Don't allow no-recurse emission as we might have to restart, which means
we will run multiple handlers and thus must ref all arguments */
@ -3495,7 +3515,7 @@ g_signal_emit_valist (gpointer instance,
if (fastpath_handler)
handler_unref_R (signal_id, instance, fastpath_handler);
SIGNAL_UNLOCK ();
SIGNAL_UNLOCK ();
if (accumulator)
g_value_unset (&accu);
@ -3533,7 +3553,7 @@ g_signal_emit_valist (gpointer instance,
g_object_unref (instance);
#endif
return;
return FALSE;
}
}
SIGNAL_UNLOCK ();
@ -3564,7 +3584,7 @@ g_signal_emit_valist (gpointer instance,
while (i--)
g_value_unset (param_values + i);
return;
return FALSE;
}
}
@ -3602,6 +3622,8 @@ g_signal_emit_valist (gpointer instance,
for (i = 0; i < n_params; i++)
g_value_unset (param_values + i);
g_value_unset (instance_and_params);
return FALSE;
}
/**
@ -3663,19 +3685,23 @@ g_signal_emit_by_name (gpointer instance,
SIGNAL_LOCK ();
signal_id = signal_parse_name (detailed_signal, itype, &detail, TRUE);
SIGNAL_UNLOCK ();
if (signal_id)
{
va_list var_args;
va_start (var_args, detailed_signal);
g_signal_emit_valist (instance, signal_id, detail, var_args);
if (signal_emit_valist_unlocked (instance, signal_id, detail, var_args))
SIGNAL_UNLOCK ();
va_end (var_args);
}
else
g_critical ("%s: signal name '%s' is invalid for instance '%p' of type '%s'",
G_STRLOC, detailed_signal, instance, g_type_name (itype));
{
SIGNAL_UNLOCK ();
g_critical ("%s: signal name '%s' is invalid for instance '%p' of type '%s'",
G_STRLOC, detailed_signal, instance, g_type_name (itype));
}
}
static gboolean