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Commit4c40995

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In array_position()/array_positions(), beware of empty input array.
These functions incautiously fetched the array's first lower boundeven when the array is zero-dimensional, thus fetching the wordafter the allocated array space. While almost always harmless,with very bad luck this could result in SIGSEGV. Fix by addingan early exit for empty input.Per bug #17920 from Alexander Lakhin.Discussion:https://postgr.es/m/17920-f7c228c627b6d02e%40postgresql.org
1 parent0553528 commit4c40995

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1 file changed

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‎src/backend/utils/adt/array_userfuncs.c‎

Lines changed: 12 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1275,7 +1275,6 @@ array_position_common(FunctionCallInfo fcinfo)
12751275
PG_RETURN_NULL();
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12771277
array=PG_GETARG_ARRAYTYPE_P(0);
1278-
element_type=ARR_ELEMTYPE(array);
12791278

12801279
/*
12811280
* We refuse to search for elements in multi-dimensional arrays, since we
@@ -1286,6 +1285,10 @@ array_position_common(FunctionCallInfo fcinfo)
12861285
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
12871286
errmsg("searching for elements in multidimensional arrays is not supported")));
12881287

1288+
/* Searching in an empty array is well-defined, though: it always fails */
1289+
if (ARR_NDIM(array)<1)
1290+
PG_RETURN_NULL();
1291+
12891292
if (PG_ARGISNULL(1))
12901293
{
12911294
/* fast return when the array doesn't have nulls */
@@ -1300,6 +1303,7 @@ array_position_common(FunctionCallInfo fcinfo)
13001303
null_search= false;
13011304
}
13021305

1306+
element_type=ARR_ELEMTYPE(array);
13031307
position= (ARR_LBOUND(array))[0]-1;
13041308

13051309
/* figure out where to start */
@@ -1425,9 +1429,6 @@ array_positions(PG_FUNCTION_ARGS)
14251429
PG_RETURN_NULL();
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14271431
array=PG_GETARG_ARRAYTYPE_P(0);
1428-
element_type=ARR_ELEMTYPE(array);
1429-
1430-
position= (ARR_LBOUND(array))[0]-1;
14311432

14321433
/*
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* We refuse to search for elements in multi-dimensional arrays, since we
@@ -1440,6 +1441,10 @@ array_positions(PG_FUNCTION_ARGS)
14401441

14411442
astate=initArrayResult(INT4OID,CurrentMemoryContext, false);
14421443

1444+
/* Searching in an empty array is well-defined, though: it always fails */
1445+
if (ARR_NDIM(array)<1)
1446+
PG_RETURN_DATUM(makeArrayResult(astate,CurrentMemoryContext));
1447+
14431448
if (PG_ARGISNULL(1))
14441449
{
14451450
/* fast return when the array doesn't have nulls */
@@ -1454,6 +1459,9 @@ array_positions(PG_FUNCTION_ARGS)
14541459
null_search= false;
14551460
}
14561461

1462+
element_type=ARR_ELEMTYPE(array);
1463+
position= (ARR_LBOUND(array))[0]-1;
1464+
14571465
/*
14581466
* We arrange to look up type info for array_create_iterator only once per
14591467
* series of calls, assuming the element type doesn't change underneath

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