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Rework perform_arith_op() in expr(1) to omit Undefined Behavior 

The current implementation of operations - + * / % could cause Undefined
Behavior and in narrow cases (INT64_MIN / -1 and INT64_MIN % -1) SIGFPE
and crash duping core.

Detected with MKSANITIZER enabled for the Undefined Behavior variation:
# eval expr '4611686018427387904 + 4611686018427387904'
/public/src.git/bin/expr/expr.y:315:12: runtime error: signed integer overflow: 4611686018427387904 + 4611686018427387904 cannot be represented in type 'long'

All bin/t_expr ATF tests pass now in a sanitized userland.

Sponsored by <The NetBSD Foundation>
This commit is contained in:
kamil 2018-06-12 18:12:18 +00:00
parent 88efda49f6
commit 7806b47917
1 changed files with 40 additions and 39 deletions
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79
bin/expr/expr.y
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@ -1,4 +1,4 @@
/* $NetBSD: expr.y,v 1.39 2016/09/05 01:00:07 sevan Exp $ */
/* $NetBSD: expr.y,v 1.40 2018/06/12 18:12:18 kamil Exp $ */
/*_
* Copyright (c) 2000 The NetBSD Foundation, Inc.
@ -32,7 +32,7 @@
%{
#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: expr.y,v 1.39 2016/09/05 01:00:07 sevan Exp $");
__RCSID("$NetBSD: expr.y,v 1.40 2018/06/12 18:12:18 kamil Exp $");
#endif /* not lint */
#include <sys/types.h>
@ -273,8 +273,7 @@ is_integer(const char *str)
static int64_t
perform_arith_op(const char *left, const char *op, const char *right)
{
int64_t res, sign, l, r;
u_int64_t temp;
int64_t res, l, r;
res = 0;
@ -307,66 +306,68 @@ perform_arith_op(const char *left, const char *op, const char *right)
switch(op[0]) {
case '+':
/*
* Do the op into an unsigned to avoid overflow and then cast
* back to check the resulting signage.
/*
* Check for over-& underflow.
*/
temp = l + r;
res = (int64_t) temp;
/* very simplistic check for over-& underflow */
if ((res < 0 && l > 0 && r > 0)
|| (res > 0 && l < 0 && r < 0))
if ((l > 0 && r <= INT64_MAX - l) ||
(l < 0 && r >= INT64_MIN - l)) {
res = l + r;
} else {
yyerror("integer overflow or underflow occurred for "
"operation '%s %s %s'", left, op, right);
}
break;
case '-':
/*
* Do the op into an unsigned to avoid overflow and then cast
* back to check the resulting signage.
/*
* Check for over-& underflow.
*/
temp = l - r;
res = (int64_t) temp;
/* very simplistic check for over-& underflow */
if ((res < 0 && l > 0 && l > r)
|| (res > 0 && l < 0 && l < r) )
if ((r > 0 && l < INT64_MIN + r) ||
(r < 0 && l > INT64_MAX + r)) {
yyerror("integer overflow or underflow occurred for "
"operation '%s %s %s'", left, op, right);
} else {
res = l - r;
}
break;
case '/':
if (r == 0)
if (r == 0)
yyerror("second argument to '%s' must not be zero", op);
if (l == INT64_MIN && r == -1)
yyerror("integer overflow or underflow occurred for "
"operation '%s %s %s'", left, op, right);
res = l / r;
break;
case '%':
if (r == 0)
yyerror("second argument to '%s' must not be zero", op);
if (l == INT64_MIN && r == -1)
yyerror("integer overflow or underflow occurred for "
"operation '%s %s %s'", left, op, right);
res = l % r;
break;
case '*':
/* shortcut */
if ((l == 0) || (r == 0)) {
res = 0;
break;
}
sign = 1;
if (l < 0)
sign *= -1;
if (r < 0)
sign *= -1;
res = l * r;
/*
* XXX: not the most portable but works on anything with 2's
* complement arithmetic. If the signs don't match or the
* result was 0 on 2's complement this overflowed.
* Check for over-& underflow.
*/
if ((res < 0 && sign > 0) || (res > 0 && sign < 0) ||
(res == 0))
/* Simplify the conditions */
if (l < 0 && r < 0 && l != INT64_MIN && r != INT64_MIN) {
l = -l;
r = -r;
}
if ((l < 0 && r < 0) ||
((l != 0 && r != 0) &&
(((l > 0 && r > 0) && (l > INT64_MAX / r)) ||
((((l < 0 && r > 0) || (l > 0 && r < 0)) &&
(r != -1 && (l < INT64_MIN / r))))))) {
yyerror("integer overflow or underflow occurred for "
"operation '%s %s %s'", left, op, right);
/* NOTREACHED */
} else {
res = l * r;
}
break;
}
return res;