ash,hush: do not segfault on $((2**63 / -1))
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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08a5dab181
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27
shell/math.c
27
shell/math.c
@ -415,10 +415,29 @@ arith_apply(arith_state_t *math_state, operator op, var_or_num_t *numstack, var_
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}
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else if (right_side_val == 0)
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return "divide by zero";
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else if (op == TOK_DIV || op == TOK_DIV_ASSIGN)
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rez /= right_side_val;
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else if (op == TOK_REM || op == TOK_REM_ASSIGN)
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rez %= right_side_val;
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else if (op == TOK_DIV || op == TOK_DIV_ASSIGN
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|| op == TOK_REM || op == TOK_REM_ASSIGN) {
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/*
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* bash 4.2.45 x86 64bit: SEGV on 'echo $((2**63 / -1))'
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*
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* MAX_NEGATIVE_INT / -1 = MAX_POSITIVE_INT+1
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* and thus is not representable.
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* Some CPUs segfault trying such op.
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* Others overfolw MAX_POSITIVE_INT+1 to
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* MAX_NEGATIVE_INT (0x7fff+1 = 0x8000).
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* Make sure to at least not SEGV here:
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*/
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if (right_side_val == -1
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&& rez << 1 == 0 /* MAX_NEGATIVE_INT or 0 */
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) {
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right_side_val = 1;
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}
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if (op == TOK_DIV || op == TOK_DIV_ASSIGN)
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rez /= right_side_val;
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else {
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rez %= right_side_val;
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}
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}
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}
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if (is_assign_op(op)) {
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