Fixed bug #72907 (null pointer deref, segfault in gc_remove_zval_from_buffer (zend_gc.c:260))

5 files changed, 63 insertions, 28 deletions

diff --git a/NEWS b/NEWS
index dca9d4f48b..608881ae65 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,10 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? 2016, PHP 5.6.26
 
+- Core:
+  . Fixed bug #72907 (null pointer deref, segfault in gc_remove_zval_from_buffer
+    (zend_gc.c:260)). (Laruence)
+
 - Streams:
   . Fixed bug #72853 (stream_set_blocking doesn't work). (Laruence)
 
diff --git a/Zend/tests/bug72907.phpt b/Zend/tests/bug72907.phpt
new file mode 100644
index 0000000000..00d9f5d183
--- /dev/null
+++ b/Zend/tests/bug72907.phpt
@@ -0,0 +1,18 @@
+--TEST--
+Bug #72907 (null pointer deref, segfault in gc_remove_zval_from_buffer (zend_gc.c:260))
+--FILE--
+<?php
+
+$a = 0;
+
+($a->a = &$E) + ($b = $a->b->i -= 0);
+
+?>
+--EXPECTF--
+Warning: Attempt to modify property of non-object in %sbug72907.php on line %d
+
+Warning: Attempt to modify property of non-object in %sbug72907.php on line %d
+
+Warning: Creating default object from empty value in %sbug72907.php on line %d
+
+Notice: Undefined property: stdClass::$i in %sbug72907.php on line %d
diff --git a/Zend/zend_execute.c b/Zend/zend_execute.c
index c7e4b926d8..b422624bb1 100644
--- a/Zend/zend_execute.c
+++ b/Zend/zend_execute.c
@@ -522,9 +522,7 @@ static void zend_assign_to_variable_reference(zval **variable_ptr_ptr, zval **va
 	zval *variable_ptr = *variable_ptr_ptr;
 	zval *value_ptr = *value_ptr_ptr;
 
-	if (variable_ptr == &EG(error_zval) || value_ptr == &EG(error_zval)) {
-		variable_ptr_ptr = &EG(uninitialized_zval_ptr);
-	} else if (variable_ptr != value_ptr) {
+	if (variable_ptr != value_ptr) {
 		if (!PZVAL_IS_REF(value_ptr)) {
 			/* break it away */
 			Z_DELREF_P(value_ptr);
diff --git a/Zend/zend_vm_def.h b/Zend/zend_vm_def.h
index 2e81f82e49..f79d8a3f9e 100644
--- a/Zend/zend_vm_def.h
+++ b/Zend/zend_vm_def.h
@@ -1817,11 +1817,14 @@ ZEND_VM_HANDLER(39, ZEND_ASSIGN_REF, VAR|CV, VAR|CV)
 	if ((OP2_TYPE == IS_VAR && UNEXPECTED(value_ptr_ptr == NULL)) ||
 	    (OP1_TYPE == IS_VAR && UNEXPECTED(variable_ptr_ptr == NULL))) {
 		zend_error_noreturn(E_ERROR, "Cannot create references to/from string offsets nor overloaded objects");
-	}
-	zend_assign_to_variable_reference(variable_ptr_ptr, value_ptr_ptr TSRMLS_CC);
-
-	if (OP2_TYPE == IS_VAR && opline->extended_value == ZEND_RETURNS_NEW) {
-		Z_DELREF_PP(variable_ptr_ptr);
+	} else if ((OP2_TYPE == IS_VAR && UNEXPECTED(*value_ptr_ptr == &EG(error_zval))) ||
+		(OP1_TYPE == IS_VAR && UNEXPECTED(*variable_ptr_ptr == &EG(error_zval)))) {
+		variable_ptr_ptr = &EG(uninitialized_zval_ptr);
+	} else {
+		zend_assign_to_variable_reference(variable_ptr_ptr, value_ptr_ptr TSRMLS_CC);
+		if (OP2_TYPE == IS_VAR && opline->extended_value == ZEND_RETURNS_NEW) {
+			Z_DELREF_PP(variable_ptr_ptr);
+		}
 	}
 
 	if (RETURN_VALUE_USED(opline)) {
diff --git a/Zend/zend_vm_execute.h b/Zend/zend_vm_execute.h
index df47bea982..a31027ee92 100644
--- a/Zend/zend_vm_execute.h
+++ b/Zend/zend_vm_execute.h
@@ -20408,11 +20408,14 @@ static int ZEND_FASTCALL  ZEND_ASSIGN_REF_SPEC_VAR_VAR_HANDLER(ZEND_OPCODE_HANDL
 	if ((IS_VAR == IS_VAR && UNEXPECTED(value_ptr_ptr == NULL)) ||
 	    (IS_VAR == IS_VAR && UNEXPECTED(variable_ptr_ptr == NULL))) {
 		zend_error_noreturn(E_ERROR, "Cannot create references to/from string offsets nor overloaded objects");
-	}
-	zend_assign_to_variable_reference(variable_ptr_ptr, value_ptr_ptr TSRMLS_CC);
-
-	if (IS_VAR == IS_VAR && opline->extended_value == ZEND_RETURNS_NEW) {
-		Z_DELREF_PP(variable_ptr_ptr);
+	} else if ((IS_VAR == IS_VAR && UNEXPECTED(*value_ptr_ptr == &EG(error_zval))) ||
+		(IS_VAR == IS_VAR && UNEXPECTED(*variable_ptr_ptr == &EG(error_zval)))) {
+		variable_ptr_ptr = &EG(uninitialized_zval_ptr);
+	} else {
+		zend_assign_to_variable_reference(variable_ptr_ptr, value_ptr_ptr TSRMLS_CC);
+		if (IS_VAR == IS_VAR && opline->extended_value == ZEND_RETURNS_NEW) {
+			Z_DELREF_PP(variable_ptr_ptr);
+		}
 	}
 
 	if (RETURN_VALUE_USED(opline)) {
@@ -23903,11 +23906,14 @@ static int ZEND_FASTCALL  ZEND_ASSIGN_REF_SPEC_VAR_CV_HANDLER(ZEND_OPCODE_HANDLE
 	if ((IS_CV == IS_VAR && UNEXPECTED(value_ptr_ptr == NULL)) ||
 	    (IS_VAR == IS_VAR && UNEXPECTED(variable_ptr_ptr == NULL))) {
 		zend_error_noreturn(E_ERROR, "Cannot create references to/from string offsets nor overloaded objects");
-	}
-	zend_assign_to_variable_reference(variable_ptr_ptr, value_ptr_ptr TSRMLS_CC);
-
-	if (IS_CV == IS_VAR && opline->extended_value == ZEND_RETURNS_NEW) {
-		Z_DELREF_PP(variable_ptr_ptr);
+	} else if ((IS_CV == IS_VAR && UNEXPECTED(*value_ptr_ptr == &EG(error_zval))) ||
+		(IS_VAR == IS_VAR && UNEXPECTED(*variable_ptr_ptr == &EG(error_zval)))) {
+		variable_ptr_ptr = &EG(uninitialized_zval_ptr);
+	} else {
+		zend_assign_to_variable_reference(variable_ptr_ptr, value_ptr_ptr TSRMLS_CC);
+		if (IS_CV == IS_VAR && opline->extended_value == ZEND_RETURNS_NEW) {
+			Z_DELREF_PP(variable_ptr_ptr);
+		}
 	}
 
 	if (RETURN_VALUE_USED(opline)) {
@@ -37721,11 +37727,14 @@ static int ZEND_FASTCALL  ZEND_ASSIGN_REF_SPEC_CV_VAR_HANDLER(ZEND_OPCODE_HANDLE
 	if ((IS_VAR == IS_VAR && UNEXPECTED(value_ptr_ptr == NULL)) ||
 	    (IS_CV == IS_VAR && UNEXPECTED(variable_ptr_ptr == NULL))) {
 		zend_error_noreturn(E_ERROR, "Cannot create references to/from string offsets nor overloaded objects");
-	}
-	zend_assign_to_variable_reference(variable_ptr_ptr, value_ptr_ptr TSRMLS_CC);
-
-	if (IS_VAR == IS_VAR && opline->extended_value == ZEND_RETURNS_NEW) {
-		Z_DELREF_PP(variable_ptr_ptr);
+	} else if ((IS_VAR == IS_VAR && UNEXPECTED(*value_ptr_ptr == &EG(error_zval))) ||
+		(IS_CV == IS_VAR && UNEXPECTED(*variable_ptr_ptr == &EG(error_zval)))) {
+		variable_ptr_ptr = &EG(uninitialized_zval_ptr);
+	} else {
+		zend_assign_to_variable_reference(variable_ptr_ptr, value_ptr_ptr TSRMLS_CC);
+		if (IS_VAR == IS_VAR && opline->extended_value == ZEND_RETURNS_NEW) {
+			Z_DELREF_PP(variable_ptr_ptr);
+		}
 	}
 
 	if (RETURN_VALUE_USED(opline)) {
@@ -40929,11 +40938,14 @@ static int ZEND_FASTCALL  ZEND_ASSIGN_REF_SPEC_CV_CV_HANDLER(ZEND_OPCODE_HANDLER
 	if ((IS_CV == IS_VAR && UNEXPECTED(value_ptr_ptr == NULL)) ||
 	    (IS_CV == IS_VAR && UNEXPECTED(variable_ptr_ptr == NULL))) {
 		zend_error_noreturn(E_ERROR, "Cannot create references to/from string offsets nor overloaded objects");
-	}
-	zend_assign_to_variable_reference(variable_ptr_ptr, value_ptr_ptr TSRMLS_CC);
-
-	if (IS_CV == IS_VAR && opline->extended_value == ZEND_RETURNS_NEW) {
-		Z_DELREF_PP(variable_ptr_ptr);
+	} else if ((IS_CV == IS_VAR && UNEXPECTED(*value_ptr_ptr == &EG(error_zval))) ||
+		(IS_CV == IS_VAR && UNEXPECTED(*variable_ptr_ptr == &EG(error_zval)))) {
+		variable_ptr_ptr = &EG(uninitialized_zval_ptr);
+	} else {
+		zend_assign_to_variable_reference(variable_ptr_ptr, value_ptr_ptr TSRMLS_CC);
+		if (IS_CV == IS_VAR && opline->extended_value == ZEND_RETURNS_NEW) {
+			Z_DELREF_PP(variable_ptr_ptr);
+		}
 	}
 
 	if (RETURN_VALUE_USED(opline)) {