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GH-50544: [C++][Gandiva] fix out-of-bounds read in round with most negative precision #50545

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GH-50544: [C++][Gandiva] fix out-of-bounds read in round with most negative precision #50545

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e0953ba
check round precision bound before negating
Arawoof06 Jul 19, 2026
f1bb2c2
Add boundary tests around the round precision range check
Arawoof06 Jul 29, 2026
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14 changes: 8 additions & 6 deletions cpp/src/gandiva/precompiled/extended_math_ops.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -324,12 +324,13 @@ gdv_int32 round_int32_int32(gdv_int32 number, gdv_int32 precision) {
if (precision >= 0) {
return number;
}
gdv_int32 abs_precision = -precision;
// This is to ensure that there is no overflow while calculating 10^precision, 9 is
// the smallest N for which 10^N does not fit into 32 bits, so we can safely return 0
if (abs_precision > 9) {
// the smallest N for which 10^N does not fit into 32 bits, so we can safely return 0.
// The bound is checked before negating because -INT32_MIN is still negative.
if (precision < -9) {
return 0;
}
gdv_int32 abs_precision = -precision;
gdv_int32 num_sign = (number > 0) ? 1 : -1;
gdv_int32 abs_number = number * num_sign;
gdv_int32 power_of_10 = static_cast<gdv_int32>(get_power_of_10(abs_precision));
Expand All @@ -349,12 +350,13 @@ gdv_int64 round_int64_int32(gdv_int64 number, gdv_int32 precision) {
if (precision >= 0) {
return number;
}
gdv_int32 abs_precision = -precision;
// This is to ensure that there is no overflow while calculating 10^precision, 19 is
// the smallest N for which 10^N does not fit into 64 bits, so we can safely return 0
if (abs_precision > 18) {
// the smallest N for which 10^N does not fit into 64 bits, so we can safely return 0.
// The bound is checked before negating because -INT32_MIN is still negative.
if (precision < -18) {
return 0;
}
gdv_int32 abs_precision = -precision;
gdv_int32 num_sign = (number > 0) ? 1 : -1;
gdv_int64 abs_number = number * num_sign;
gdv_int64 power_of_10 = get_power_of_10(abs_precision);
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12 changes: 12 additions & 0 deletions cpp/src/gandiva/precompiled/extended_math_ops_test.cc
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Expand Up @@ -203,6 +203,18 @@ TEST(TestExtendedMathOps, TestRound) {
EXPECT_EQ(round_int64_int32(-23453462343, -4), -23453460000);
EXPECT_EQ(round_int64_int32(-23453462343, -5), -23453500000);
EXPECT_EQ(round_int64_int32(345353425343, -12), 0);

// The last in-range precision still rounds; one past it returns 0. These guard
// against an off-by-one in the range check at both overloads' boundary.
EXPECT_EQ(round_int32_int32(1234567890, -9), 1000000000);
EXPECT_EQ(round_int32_int32(1234567890, -10), 0);
EXPECT_EQ(round_int64_int32(1234567890123456789, -18), 1000000000000000000);
EXPECT_EQ(round_int64_int32(1234567890123456789, -19), 0);

// The most negative precision must be rejected by the range check rather than
// negated into an out-of-range table index.
EXPECT_EQ(round_int32_int32(1234, std::numeric_limits<int32_t>::min()), 0);
EXPECT_EQ(round_int64_int32(345353425343, std::numeric_limits<int32_t>::min()), 0);

@Reranko05 Reranko05 Jul 24, 2026

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Would it make sense to also add tests for the -9/-10 boundary (and -18/-19 for the int64 overload)? They could help catch any future off-by-one regressions around the new range check.

@Arawoof06 Arawoof06 Jul 29, 2026

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Good idea, added them. There's now a -9/-10 pair for the int32 overload and -18/-19 for the int64 one, so the last in-range precision still rounds and one past it returns 0. That pins the boundary against any future off-by-one.

}

TEST(TestExtendedMathOps, TestTruncate) {
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