Prevent integer overflows in array subscripting calculations.

While we were (mostly) careful about ensuring that the dimensions of
arrays aren't large enough to cause integer overflow, the lower bound
values were generally not checked.  This allows situations where
lower_bound + dimension overflows an integer.  It seems that that's
harmless so far as array reading is concerned, except that array
elements with subscripts notionally exceeding INT_MAX are inaccessible.
However, it confuses various array-assignment logic, resulting in a
potential for memory stomps.

Fix by adding checks that array lower bounds aren't large enough to
cause lower_bound + dimension to overflow.  (Note: this results in
disallowing cases where the last subscript position would be exactly
INT_MAX.  In principle we could probably allow that, but there's a lot
of code that computes lower_bound + dimension and would need adjustment.
It seems doubtful that it's worth the trouble/risk to allow it.)

Somewhat independently of that, array_set_element() was careless
about possible overflow when checking the subscript of a fixed-length
array, creating a different route to memory stomps.  Fix that too.

Security: CVE-2021-32027

diff --git a/src/backend/executor/execExprInterp.c b/src/backend/executor/execExprInterp.c
index 094e22d3923a94132e52156ad570bcc5b83b5184..a9ed98ae48524439d9a47f1ee922b4132b9c4ea6 100644 (file)
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -2828,6 +2828,10 @@ ExecEvalArrayExpr(ExprState *state, ExprEvalStep *op)
            lbs[i] = elem_lbs[i - 1];
        }
 
+       /* check for subscript overflow */
+       (void) ArrayGetNItems(ndims, dims);
+       ArrayCheckBounds(ndims, dims, lbs);
+
        if (havenulls)
        {
            dataoffset = ARR_OVERHEAD_WITHNULLS(ndims, nitems);

diff --git a/src/backend/utils/adt/array_userfuncs.c b/src/backend/utils/adt/array_userfuncs.c
index a2793bfae32a9a49001afd8e214b42a010f355ff..42503525b88f578efc7fdba74ccc425f12d5ff13 100644 (file)
--- a/src/backend/utils/adt/array_userfuncs.c
+++ b/src/backend/utils/adt/array_userfuncs.c
@@ -411,6 +411,7 @@ array_cat(PG_FUNCTION_ARGS)
 
    /* Do this mainly for overflow checking */
    nitems = ArrayGetNItems(ndims, dims);
+   ArrayCheckBounds(ndims, dims, lbs);
 
    /* build the result array */
    ndatabytes = ndatabytes1 + ndatabytes2;

diff --git a/src/backend/utils/adt/arrayfuncs.c b/src/backend/utils/adt/arrayfuncs.c
index 17a16b4c5ccfa62b263c0781f287fc4fc0f8266d..04d487c544232b4f1a5098976464d4ccc0769b70 100644 (file)
--- a/src/backend/utils/adt/arrayfuncs.c
+++ b/src/backend/utils/adt/arrayfuncs.c
@@ -372,6 +372,8 @@ array_in(PG_FUNCTION_ARGS)
 
    /* This checks for overflow of the array dimensions */
    nitems = ArrayGetNItems(ndim, dim);
+   ArrayCheckBounds(ndim, dim, lBound);
+
    /* Empty array? */
    if (nitems == 0)
        PG_RETURN_ARRAYTYPE_P(construct_empty_array(element_type));
@@ -1342,24 +1344,11 @@ array_recv(PG_FUNCTION_ARGS)
    {
        dim[i] = pq_getmsgint(buf, 4);
        lBound[i] = pq_getmsgint(buf, 4);
-
-       /*
-        * Check overflow of upper bound. (ArrayGetNItems() below checks that
-        * dim[i] >= 0)
-        */
-       if (dim[i] != 0)
-       {
-           int         ub = lBound[i] + dim[i] - 1;
-
-           if (lBound[i] > ub)
-               ereport(ERROR,
-                       (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
-                        errmsg("integer out of range")));
-       }
    }
 
    /* This checks for overflow of array dimensions */
    nitems = ArrayGetNItems(ndim, dim);
+   ArrayCheckBounds(ndim, dim, lBound);
 
    /*
     * We arrange to look up info about element type, including its receive
@@ -2265,7 +2254,7 @@ array_set_element(Datum arraydatum,
                    (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                     errmsg("wrong number of array subscripts")));
 
-       if (indx[0] < 0 || indx[0] * elmlen >= arraytyplen)
+       if (indx[0] < 0 || indx[0] >= arraytyplen / elmlen)
            ereport(ERROR,
                    (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                     errmsg("array subscript out of range")));
@@ -2380,10 +2369,13 @@ array_set_element(Datum arraydatum,
        }
    }
 
+   /* This checks for overflow of the array dimensions */
+   newnitems = ArrayGetNItems(ndim, dim);
+   ArrayCheckBounds(ndim, dim, lb);
+
    /*
     * Compute sizes of items and areas to copy
     */
-   newnitems = ArrayGetNItems(ndim, dim);
    if (newhasnulls)
        overheadlen = ARR_OVERHEAD_WITHNULLS(ndim, newnitems);
    else
@@ -2641,6 +2633,13 @@ array_set_element_expanded(Datum arraydatum,
        }
    }
 
+   /* Check for overflow of the array dimensions */
+   if (dimschanged)
+   {
+       (void) ArrayGetNItems(ndim, dim);
+       ArrayCheckBounds(ndim, dim, lb);
+   }
+
    /* Now we can calculate linear offset of target item in array */
    offset = ArrayGetOffset(nSubscripts, dim, lb, indx);
 
@@ -2960,6 +2959,7 @@ array_set_slice(Datum arraydatum,
 
    /* Do this mainly to check for overflow */
    nitems = ArrayGetNItems(ndim, dim);
+   ArrayCheckBounds(ndim, dim, lb);
 
    /*
     * Make sure source array has enough entries.  Note we ignore the shape of
@@ -3374,7 +3374,9 @@ construct_md_array(Datum *elems,
                 errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)",
                        ndims, MAXDIM)));
 
+   /* This checks for overflow of the array dimensions */
    nelems = ArrayGetNItems(ndims, dims);
+   ArrayCheckBounds(ndims, dims, lbs);
 
    /* if ndims <= 0 or any dims[i] == 0, return empty array */
    if (nelems <= 0)
@@ -5449,6 +5451,10 @@ makeArrayResultArr(ArrayBuildStateArr *astate,
        int         dataoffset,
                    nbytes;
 
+       /* Check for overflow of the array dimensions */
+       (void) ArrayGetNItems(astate->ndims, astate->dims);
+       ArrayCheckBounds(astate->ndims, astate->dims, astate->lbs);
+
        /* Compute required space */
        nbytes = astate->nbytes;
        if (astate->nullbitmap != NULL)
@@ -5878,7 +5884,9 @@ array_fill_internal(ArrayType *dims, ArrayType *lbs,
        lbsv = deflbs;
    }
 
+   /* This checks for overflow of the array dimensions */
    nitems = ArrayGetNItems(ndims, dimv);
+   ArrayCheckBounds(ndims, dimv, lbsv);
 
    /* fast track for empty array */
    if (nitems <= 0)

diff --git a/src/backend/utils/adt/arrayutils.c b/src/backend/utils/adt/arrayutils.c
index 2a6a05718f8e43e131bc2e3b03d0e95e8091b5d3..6988edd93619c5c0495b0160ecfb2ec3c6144df6 100644 (file)
--- a/src/backend/utils/adt/arrayutils.c
+++ b/src/backend/utils/adt/arrayutils.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "catalog/pg_type.h"
+#include "common/int.h"
 #include "utils/array.h"
 #include "utils/builtins.h"
 #include "utils/memutils.h"
@@ -111,6 +112,36 @@ ArrayGetNItems(int ndim, const int *dims)
    return (int) ret;
 }
 
+/*
+ * Verify sanity of proposed lower-bound values for an array
+ *
+ * The lower-bound values must not be so large as to cause overflow when
+ * calculating subscripts, e.g. lower bound 2147483640 with length 10
+ * must be disallowed.  We actually insist that dims[i] + lb[i] be
+ * computable without overflow, meaning that an array with last subscript
+ * equal to INT_MAX will be disallowed.
+ *
+ * It is assumed that the caller already called ArrayGetNItems, so that
+ * overflowed (negative) dims[] values have been eliminated.
+ */
+void
+ArrayCheckBounds(int ndim, const int *dims, const int *lb)
+{
+   int         i;
+
+   for (i = 0; i < ndim; i++)
+   {
+       /* PG_USED_FOR_ASSERTS_ONLY prevents variable-isn't-read warnings */
+       int32       sum PG_USED_FOR_ASSERTS_ONLY;
+
+       if (pg_add_s32_overflow(dims[i], lb[i], &sum))
+           ereport(ERROR,
+                   (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                    errmsg("array lower bound is too large: %d",
+                           lb[i])));
+   }
+}
+
 /*
  * Compute ranges (sub-array dimensions) for an array slice
  *

diff --git a/src/include/utils/array.h b/src/include/utils/array.h
index 937caf7565b02e21f9c1d2c4202dad869bb1b206..4ae6c3be2f8b57afa38c19af2779f67c782e4efc 100644 (file)
--- a/src/include/utils/array.h
+++ b/src/include/utils/array.h
@@ -443,6 +443,7 @@ extern void array_free_iterator(ArrayIterator iterator);
 extern int ArrayGetOffset(int n, const int *dim, const int *lb, const int *indx);
 extern int ArrayGetOffset0(int n, const int *tup, const int *scale);
 extern int ArrayGetNItems(int ndim, const int *dims);
+extern void ArrayCheckBounds(int ndim, const int *dims, const int *lb);
 extern void mda_get_range(int n, int *span, const int *st, const int *endp);
 extern void mda_get_prod(int n, const int *range, int *prod);
 extern void mda_get_offset_values(int n, int *dist, const int *prod, const int *span);