Guard against overflow in interval_mul() and interval_div().

Commits 146604ec43 and a898b409f6 added overflow checks to
interval_mul(), but not to interval_div(), which contains almost
identical code, and so is susceptible to the same kinds of
overflows. In addition, those checks did not catch all possible
overflow conditions.

Add additional checks to the "cascade down" code in interval_mul(),
and copy all the overflow checks over to the corresponding code in
interval_div(), so that they both generate "interval out of range"
errors, rather than returning bogus results.

Given that these errors are relatively easy to hit, back-patch to all
supported branches.

Per bug #18200 from Alexander Lakhin, and subsequent investigation.

Discussion: https://postgr.es/m/18200-5ea288c7b2d504b1%40postgresql.org

1 files changed, 49 insertions, 21 deletions

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index 3e7c77ee48f..fbc6bad20d6 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -22,6 +22,7 @@
 
 #include "access/xact.h"
 #include "catalog/pg_type.h"
+#include "common/int.h"
 #include "common/int128.h"
 #include "funcapi.h"
 #include "libpq/pqformat.h"
@@ -3189,19 +3190,13 @@ interval_mul(PG_FUNCTION_ARGS)
 	result = (Interval *) palloc(sizeof(Interval));
 
 	result_double = span->month * factor;
-	if (isnan(result_double) ||
-		result_double > INT_MAX || result_double < INT_MIN)
-		ereport(ERROR,
-				(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
-				 errmsg("interval out of range")));
+	if (isnan(result_double) || !FLOAT8_FITS_IN_INT32(result_double))
+		goto out_of_range;
 	result->month = (int32) result_double;
 
 	result_double = span->day * factor;
-	if (isnan(result_double) ||
-		result_double > INT_MAX || result_double < INT_MIN)
-		ereport(ERROR,
-				(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
-				 errmsg("interval out of range")));
+	if (isnan(result_double) || !FLOAT8_FITS_IN_INT32(result_double))
+		goto out_of_range;
 	result->day = (int32) result_double;
 
 	/*
@@ -3235,20 +3230,30 @@ interval_mul(PG_FUNCTION_ARGS)
 	 */
 	if (Abs(sec_remainder) >= SECS_PER_DAY)
 	{
-		result->day += (int) (sec_remainder / SECS_PER_DAY);
+		if (pg_add_s32_overflow(result->day,
+								(int) (sec_remainder / SECS_PER_DAY),
+								&result->day))
+			goto out_of_range;
 		sec_remainder -= (int) (sec_remainder / SECS_PER_DAY) * SECS_PER_DAY;
 	}
 
 	/* cascade units down */
-	result->day += (int32) month_remainder_days;
+	if (pg_add_s32_overflow(result->day, (int32) month_remainder_days,
+							&result->day))
+		goto out_of_range;
 	result_double = rint(span->time * factor + sec_remainder * USECS_PER_SEC);
 	if (isnan(result_double) || !FLOAT8_FITS_IN_INT64(result_double))
-		ereport(ERROR,
-				(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
-				 errmsg("interval out of range")));
+		goto out_of_range;
 	result->time = (int64) result_double;
 
 	PG_RETURN_INTERVAL_P(result);
+
+out_of_range:
+	ereport(ERROR,
+			errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+			errmsg("interval out of range"));
+
+	PG_RETURN_NULL();			/* keep compiler quiet */
 }
 
 Datum
@@ -3267,7 +3272,8 @@ interval_div(PG_FUNCTION_ARGS)
 	Interval   *span = PG_GETARG_INTERVAL_P(0);
 	float8		factor = PG_GETARG_FLOAT8(1);
 	double		month_remainder_days,
-				sec_remainder;
+				sec_remainder,
+				result_double;
 	int32		orig_month = span->month,
 				orig_day = span->day;
 	Interval   *result;
@@ -3279,8 +3285,15 @@ interval_div(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_DIVISION_BY_ZERO),
 				 errmsg("division by zero")));
 
-	result->month = (int32) (span->month / factor);
-	result->day = (int32) (span->day / factor);
+	result_double = span->month / factor;
+	if (isnan(result_double) || !FLOAT8_FITS_IN_INT32(result_double))
+		goto out_of_range;
+	result->month = (int32) result_double;
+
+	result_double = span->day / factor;
+	if (isnan(result_double) || !FLOAT8_FITS_IN_INT32(result_double))
+		goto out_of_range;
+	result->day = (int32) result_double;
 
 	/*
 	 * Fractional months full days into days.  See comment in interval_mul().
@@ -3292,15 +3305,30 @@ interval_div(PG_FUNCTION_ARGS)
 	sec_remainder = TSROUND(sec_remainder);
 	if (Abs(sec_remainder) >= SECS_PER_DAY)
 	{
-		result->day += (int) (sec_remainder / SECS_PER_DAY);
+		if (pg_add_s32_overflow(result->day,
+								(int) (sec_remainder / SECS_PER_DAY),
+								&result->day))
+			goto out_of_range;
 		sec_remainder -= (int) (sec_remainder / SECS_PER_DAY) * SECS_PER_DAY;
 	}
 
 	/* cascade units down */
-	result->day += (int32) month_remainder_days;
-	result->time = rint(span->time / factor + sec_remainder * USECS_PER_SEC);
+	if (pg_add_s32_overflow(result->day, (int32) month_remainder_days,
+							&result->day))
+		goto out_of_range;
+	result_double = rint(span->time / factor + sec_remainder * USECS_PER_SEC);
+	if (isnan(result_double) || !FLOAT8_FITS_IN_INT64(result_double))
+		goto out_of_range;
+	result->time = (int64) result_double;
 
 	PG_RETURN_INTERVAL_P(result);
+
+out_of_range:
+	ereport(ERROR,
+			errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+			errmsg("interval out of range"));
+
+	PG_RETURN_NULL();			/* keep compiler quiet */
 }