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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.
str_size_and_int64
Ard Biesheuvel 12 years ago
parent
commit
60d2e70c06
  1. 9
      Zend/zend_operators.h

9
Zend/zend_operators.h

@ -643,13 +643,18 @@ 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

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