Fix integer overflow in array_agg(), when the array grows too large

If you accumulate many arrays full of NULLs, you could overflow
'nitems', before reaching the MaxAllocSize limit on the allocations.
Add an explicit check that the number of items doesn't grow too large.
With more than MaxArraySize items, getting the final result with
makeArrayResultArr() would fail anyway, so better to error out early.

Reported-by: Xint Code
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Backpatch-through: 14
Security: CVE-2026-6473

diff --git a/src/backend/utils/adt/arrayfuncs.c b/src/backend/utils/adt/arrayfuncs.c
index 2933a95c4a59c35dca0938d6c2dab0b130008e3b..13eed22dd6ac8d26b1e01776b2ba59fd4ae68787 100644 (file)
--- a/src/backend/utils/adt/arrayfuncs.c
+++ b/src/backend/utils/adt/arrayfuncs.c
@@ -5576,6 +5576,7 @@ accumArrayResultArr(ArrayBuildStateArr *astate,
                                ndatabytes;
        char       *data;
        int                     i;
+       int                     newnitems;
 
        /*
         * We disallow accumulating null subarrays.  Another plausible definition
@@ -5605,6 +5606,14 @@ accumArrayResultArr(ArrayBuildStateArr *astate,
        nitems = ArrayGetNItems(ndims, dims);
        ndatabytes = ARR_SIZE(arg) - ARR_DATA_OFFSET(arg);
 
+       /* Check that the array doesn't grow too large */
+       newnitems = astate->nitems + nitems;
+       if (newnitems > MaxArraySize)
+               ereport(ERROR,
+                               (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                                errmsg("array size exceeds the maximum allowed (%zu)",
+                                               MaxArraySize)));
+
        if (astate->ndims == 0)
        {
                /* First input; check/save the dimensionality info */
@@ -5670,8 +5679,6 @@ accumArrayResultArr(ArrayBuildStateArr *astate,
        /* Deal with null bitmap if needed */
        if (astate->nullbitmap || ARR_HASNULL(arg))
        {
-               int                     newnitems = astate->nitems + nitems;
-
                if (astate->nullbitmap == NULL)
                {
                        /*
@@ -5695,7 +5702,7 @@ accumArrayResultArr(ArrayBuildStateArr *astate,
                                                  nitems);
        }
 
-       astate->nitems += nitems;
+       astate->nitems = newnitems;
        astate->dims[0] += 1;
 
        MemoryContextSwitchTo(oldcontext);