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 a73e3dff2e50580bef082045bda29c6f22e1ea6d..23eef6043d84c67cd85dd81ed3199148f543f67a 100644 (file)
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -2731,6 +2731,10 @@ 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 470a480fdd06339d11c81363641422b916e9f007..8689a56e8c783cb0330f561a9c3b60df4cf867df 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 94c429684cb08f08e2be61b476816f7f5a19564c..376efb83496cfc045bedec30c379b44490fd6763 100644 (file)
--- a/src/backend/utils/adt/arrayfuncs.c
+++ b/src/backend/utils/adt/arrayfuncs.c
@@ -371,6 +371,8 @@ 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));
@@ -1320,24 +1322,11 @@ 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
@@ -2242,7 +2231,7 @@ 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")));
@@ -2357,10 +2346,13 @@ 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
@@ -2615,6 +2607,13 @@ 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);
 
@@ -2933,6 +2932,7 @@ 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
@@ -3347,7 +3347,9 @@ 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)
@@ -5421,6 +5423,10 @@ 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)
@@ -5850,7 +5856,9 @@ 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 6170e35ac255721fa394fbd8109f051ede7218d2..34b337aac4ffe436bdd479cbe9c1687fe0a6aedb 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 b441eb452b94a71c92e2f174a6e657a6b57e7e7b..870324b3f484b5eac88d3b138dbf5fa811dede59 100644 (file)
--- a/src/include/utils/array.h
+++ b/src/include/utils/array.h
@@ -438,6 +438,7 @@ 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);