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 41d3a1ba224c5ccccc6fdf30177d7e7aba4616cc..75cc4eeca52db3ffefc5549c0917bcea4d68bc7c 100644 (file)
--- a/src/backend/utils/adt/arrayfuncs.c
+++ b/src/backend/utils/adt/arrayfuncs.c
@@ -5555,6 +5555,7 @@ accumArrayResultArr(ArrayBuildStateArr *astate,
                                ndatabytes;
        char       *data;
        int                     i;
+       int                     newnitems;
 
        /*
         * We disallow accumulating null subarrays.  Another plausible definition
@@ -5584,6 +5585,14 @@ 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 */
@@ -5649,8 +5658,6 @@ accumArrayResultArr(ArrayBuildStateArr *astate,
        /* Deal with null bitmap if needed */
        if (astate->nullbitmap || ARR_HASNULL(arg))
        {
-               int                     newnitems = astate->nitems + nitems;
-
                if (astate->nullbitmap == NULL)
                {
                        /*
@@ -5674,7 +5681,7 @@ accumArrayResultArr(ArrayBuildStateArr *astate,
                                                  nitems);
        }
 
-       astate->nitems += nitems;
+       astate->nitems = newnitems;
        astate->dims[0] += 1;
 
        MemoryContextSwitchTo(oldcontext);