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 f2a52f62135bfcb218a99d1bd552a0a97d9cc1b0..b5f5b735f81ffcbdafe3633379ea4d474ef19c61 100644 (file)
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -2286,6 +2286,10 @@ 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 87d79f3f98b8b849cd39418345b68e6b890fcb2f..6746f514eda2cde7aa0af5691c4c6f69c8e7781e 100644 (file)
--- a/src/backend/utils/adt/array_userfuncs.c
+++ b/src/backend/utils/adt/array_userfuncs.c
@@ -416,6 +416,7 @@ 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 944a77ebbc2f106d48a6add7154cda3a3a3011bc..553c517379a3279965f4e4fc2660cfbe66661b1a 100644 (file)
--- a/src/backend/utils/adt/arrayfuncs.c
+++ b/src/backend/utils/adt/arrayfuncs.c
@@ -370,6 +370,8 @@ 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));
@@ -1319,24 +1321,11 @@ array_recv(PG_FUNCTION_ARGS)
    {
        dim[i] = pq_getmsgint(buf, 4);
        lBound[i] = pq_getmsgint(buf, 4);
-
-       /*
-        * Check overflow of upper bound. (ArrayNItems() 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
@@ -2241,7 +2230,7 @@ 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")));
@@ -2356,10 +2345,13 @@ 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
@@ -2614,6 +2606,13 @@ 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);
 
@@ -2932,6 +2931,7 @@ 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
@@ -3377,7 +3377,9 @@ construct_md_array(Datum *elems,
    if (ndims == 0)
        return construct_empty_array(elmtype);
 
+   /* This checks for overflow of the array dimensions */
    nelems = ArrayGetNItems(ndims, dims);
+   ArrayCheckBounds(ndims, dims, lbs);
 
    /* compute required space */
    nbytes = 0;
@@ -5370,6 +5372,10 @@ 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)
@@ -5799,7 +5805,9 @@ 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 27b24703b0bfd193d8c8cc5536d8de53dff60ffa..f7c6a5167dd4b068594b12819d10ef6749dd5c0f 100644 (file)
--- a/src/backend/utils/adt/arrayutils.c
+++ b/src/backend/utils/adt/arrayutils.c
@@ -111,6 +111,33 @@ 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++)
+   {
+       if (dims[i] + lb[i] < lb[i])
+           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 eb02258a8f71eaa6cef637fc1324b7c049149192..905f6b05f116016447b5998187a0b4c803842e7d 100644 (file)
--- a/src/include/utils/array.h
+++ b/src/include/utils/array.h
@@ -433,6 +433,7 @@ 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);