From 4624aad61a313520d6542a210680088cec644dca Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Thu, 4 May 2023 11:48:23 -0400 Subject: [PATCH] In array_position()/array_positions(), beware of empty input array. These functions incautiously fetched the array's first lower bound even when the array is zero-dimensional, thus fetching the word after the allocated array space. While almost always harmless, with very bad luck this could result in SIGSEGV. Fix by adding an early exit for empty input. Per bug #17920 from Alexander Lakhin. Discussion: https://postgr.es/m/17920-f7c228c627b6d02e%40postgresql.org --- src/backend/utils/adt/array_userfuncs.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/src/backend/utils/adt/array_userfuncs.c b/src/backend/utils/adt/array_userfuncs.c index c0abc3fb3e..bfcccea46a 100644 --- a/src/backend/utils/adt/array_userfuncs.c +++ b/src/backend/utils/adt/array_userfuncs.c @@ -651,7 +651,6 @@ array_position_common(FunctionCallInfo fcinfo) PG_RETURN_NULL(); array = PG_GETARG_ARRAYTYPE_P(0); - element_type = ARR_ELEMTYPE(array); /* * We refuse to search for elements in multi-dimensional arrays, since we @@ -662,6 +661,10 @@ array_position_common(FunctionCallInfo fcinfo) (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("searching for elements in multidimensional arrays is not supported"))); + /* Searching in an empty array is well-defined, though: it always fails */ + if (ARR_NDIM(array) < 1) + PG_RETURN_NULL(); + if (PG_ARGISNULL(1)) { /* fast return when the array doesn't have nulls */ @@ -676,6 +679,7 @@ array_position_common(FunctionCallInfo fcinfo) null_search = false; } + element_type = ARR_ELEMTYPE(array); position = (ARR_LBOUND(array))[0] - 1; /* figure out where to start */ @@ -801,9 +805,6 @@ array_positions(PG_FUNCTION_ARGS) PG_RETURN_NULL(); array = PG_GETARG_ARRAYTYPE_P(0); - element_type = ARR_ELEMTYPE(array); - - position = (ARR_LBOUND(array))[0] - 1; /* * We refuse to search for elements in multi-dimensional arrays, since we @@ -816,6 +817,10 @@ array_positions(PG_FUNCTION_ARGS) astate = initArrayResult(INT4OID, CurrentMemoryContext, false); + /* Searching in an empty array is well-defined, though: it always fails */ + if (ARR_NDIM(array) < 1) + PG_RETURN_DATUM(makeArrayResult(astate, CurrentMemoryContext)); + if (PG_ARGISNULL(1)) { /* fast return when the array doesn't have nulls */ @@ -830,6 +835,9 @@ array_positions(PG_FUNCTION_ARGS) null_search = false; } + element_type = ARR_ELEMTYPE(array); + position = (ARR_LBOUND(array))[0] - 1; + /* * We arrange to look up type info for array_create_iterator only once per * series of calls, assuming the element type doesn't change underneath