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 6eb9f2933182362b08a517b420685e5059be38b7..fee1ebd160ae2500604ff6a82b6d6db7866d5fb9 100644 (file)
--- a/src/backend/utils/adt/arrayfuncs.c
+++ b/src/backend/utils/adt/arrayfuncs.c
@@ -5542,6 +5542,7 @@ accumArrayResultArr(ArrayBuildStateArr *astate,
                                ndatabytes;
        char       *data;
        int                     i;
+       int                     newnitems;
 
        /*
         * We disallow accumulating null subarrays.  Another plausible definition
@@ -5571,6 +5572,14 @@ 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 */
@@ -5636,8 +5645,6 @@ accumArrayResultArr(ArrayBuildStateArr *astate,
        /* Deal with null bitmap if needed */
        if (astate->nullbitmap || ARR_HASNULL(arg))
        {
-               int                     newnitems = astate->nitems + nitems;
-
                if (astate->nullbitmap == NULL)
                {
                        /*
@@ -5661,7 +5668,7 @@ accumArrayResultArr(ArrayBuildStateArr *astate,
                                                  nitems);
        }
 
-       astate->nitems += nitems;
+       astate->nitems = newnitems;
        astate->dims[0] += 1;
 
        MemoryContextSwitchTo(oldcontext);