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From 60d2e70c062e436a6c6cd3c8a17469a083a38b46 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date: Tue, 10 Dec 2013 12:07:46 +0100
Subject: [PATCH] Zend: fix overflow handling bug in non-x86
fast_add_function()
The 'result' argument of fast_add_function() may alias with either
of its operands (or both). Take care not to write to 'result' before
reading op1 and op2.
---
Zend/zend_operators.h | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/Zend/zend_operators.h b/Zend/zend_operators.h
index 0152e03..5c6fc86 100644
--- a/Zend/zend_operators.h
+++ b/Zend/zend_operators.h
@@ -640,13 +640,18 @@ static zend_always_inline int fast_add_function(zval *result, zval *op1, zval *o
"n"(ZVAL_OFFSETOF_TYPE)
: "rax","cc");
#else
- Z_LVAL_P(result) = Z_LVAL_P(op1) + Z_LVAL_P(op2);
+ /*
+ * 'result' may alias with op1 or op2, so we need to
+ * ensure that 'result' is not updated until after we
+ * have read the values of op1 and op2.
+ */
if (UNEXPECTED((Z_LVAL_P(op1) & LONG_SIGN_MASK) == (Z_LVAL_P(op2) & LONG_SIGN_MASK)
- && (Z_LVAL_P(op1) & LONG_SIGN_MASK) != (Z_LVAL_P(result) & LONG_SIGN_MASK))) {
+ && (Z_LVAL_P(op1) & LONG_SIGN_MASK) != ((Z_LVAL_P(op1) + Z_LVAL_P(op2)) & LONG_SIGN_MASK))) {
Z_DVAL_P(result) = (double) Z_LVAL_P(op1) + (double) Z_LVAL_P(op2);
Z_TYPE_P(result) = IS_DOUBLE;
} else {
+ Z_LVAL_P(result) = Z_LVAL_P(op1) + Z_LVAL_P(op2);
Z_TYPE_P(result) = IS_LONG;
}
#endif
--
1.8.4.3
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