Predict integer overflow to avoid buffer overruns.

Several functions, mostly type input functions, calculated an allocation
size such that the calculation wrapped to a small positive value when
arguments implied a sufficiently-large requirement.  Writes past the end
of the inadvertent small allocation followed shortly thereafter.
Coverity identified the path_in() vulnerability; code inspection led to
the rest.  In passing, add check_stack_depth() to prevent stack overflow
in related functions.

Back-patch to 8.4 (all supported versions).  The non-comment hstore
changes touch code that did not exist in 8.4, so that part stops at 9.0.

Noah Misch and Heikki Linnakangas, reviewed by Tom Lane.

Security: CVE-2014-0064

15 files changed, 169 insertions, 19 deletions

diff --git a/contrib/hstore/hstore.h b/contrib/hstore/hstore.h
index 8906397ad23..4e55f6e5e28 100644
--- a/contrib/hstore/hstore.h
+++ b/contrib/hstore/hstore.h
@@ -49,9 +49,12 @@ typedef struct
 } HStore;
 
 /*
- * it's not possible to get more than 2^28 items into an hstore,
- * so we reserve the top few bits of the size field. See hstore_compat.c
- * for one reason why.	Some bits are left for future use here.
+ * It's not possible to get more than 2^28 items into an hstore, so we reserve
+ * the top few bits of the size field.  See hstore_compat.c for one reason
+ * why.  Some bits are left for future use here.  MaxAllocSize makes the
+ * practical count limit slightly more than 2^28 / 3, or INT_MAX / 24, the
+ * limit for an hstore full of 4-byte keys and null values.  Therefore, we
+ * don't explicitly check the format-imposed limit.
  */
 #define HS_FLAG_NEWVERSION 0x80000000
 
@@ -59,6 +62,12 @@ typedef struct
 #define HS_SETCOUNT(hsp_,c_) ((hsp_)->size_ = (c_) | HS_FLAG_NEWVERSION)
 
 
+/*
+ * "x" comes from an existing HS_COUNT() (as discussed, <= INT_MAX/24) or a
+ * Pairs array length (due to MaxAllocSize, <= INT_MAX/40).  "lenstr" is no
+ * more than INT_MAX, that extreme case arising in hstore_from_arrays().
+ * Therefore, this calculation is limited to about INT_MAX / 5 + INT_MAX.
+ */
 #define HSHRDSIZE	(sizeof(HStore))
 #define CALCDATASIZE(x, lenstr) ( (x) * 2 * sizeof(HEntry) + HSHRDSIZE + (lenstr) )
 
diff --git a/contrib/hstore/hstore_io.c b/contrib/hstore/hstore_io.c
index 0d6f0b6b138..7b49ae3525e 100644
--- a/contrib/hstore/hstore_io.c
+++ b/contrib/hstore/hstore_io.c
@@ -11,6 +11,7 @@
 #include "funcapi.h"
 #include "libpq/pqformat.h"
 #include "utils/lsyscache.h"
+#include "utils/memutils.h"
 #include "utils/typcache.h"
 
 #include "hstore.h"
@@ -438,6 +439,11 @@ hstore_recv(PG_FUNCTION_ARGS)
 		PG_RETURN_POINTER(out);
 	}
 
+	if (pcount < 0 || pcount > MaxAllocSize / sizeof(Pairs))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+			  errmsg("number of pairs (%d) exceeds the maximum allowed (%d)",
+					 pcount, (int) (MaxAllocSize / sizeof(Pairs)))));
 	pairs = palloc(pcount * sizeof(Pairs));
 
 	for (i = 0; i < pcount; ++i)
@@ -553,6 +559,13 @@ hstore_from_arrays(PG_FUNCTION_ARGS)
 					  TEXTOID, -1, false, 'i',
 					  &key_datums, &key_nulls, &key_count);
 
+	/* see discussion in hstoreArrayToPairs() */
+	if (key_count > MaxAllocSize / sizeof(Pairs))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+			  errmsg("number of pairs (%d) exceeds the maximum allowed (%d)",
+					 key_count, (int) (MaxAllocSize / sizeof(Pairs)))));
+
 	/* value_array might be NULL */
 
 	if (PG_ARGISNULL(1))
@@ -675,6 +688,13 @@ hstore_from_array(PG_FUNCTION_ARGS)
 
 	count = in_count / 2;
 
+	/* see discussion in hstoreArrayToPairs() */
+	if (count > MaxAllocSize / sizeof(Pairs))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+			  errmsg("number of pairs (%d) exceeds the maximum allowed (%d)",
+					 count, (int) (MaxAllocSize / sizeof(Pairs)))));
+
 	pairs = palloc(count * sizeof(Pairs));
 
 	for (i = 0; i < count; ++i)
@@ -806,6 +826,7 @@ hstore_from_record(PG_FUNCTION_ARGS)
 		my_extra->ncolumns = ncolumns;
 	}
 
+	Assert(ncolumns <= MaxTupleAttributeNumber);		/* thus, no overflow */
 	pairs = palloc(ncolumns * sizeof(Pairs));
 
 	if (rec)
diff --git a/contrib/hstore/hstore_op.c b/contrib/hstore/hstore_op.c
index 5b278c14ffe..a60e72ee6cc 100644
--- a/contrib/hstore/hstore_op.c
+++ b/contrib/hstore/hstore_op.c
@@ -9,6 +9,7 @@
 #include "catalog/pg_type.h"
 #include "funcapi.h"
 #include "utils/builtins.h"
+#include "utils/memutils.h"
 
 #include "hstore.h"
 
@@ -91,6 +92,19 @@ hstoreArrayToPairs(ArrayType *a, int *npairs)
 		return NULL;
 	}
 
+	/*
+	 * A text array uses at least eight bytes per element, so any overflow in
+	 * "key_count * sizeof(Pairs)" is small enough for palloc() to catch.
+	 * However, credible improvements to the array format could invalidate
+	 * that assumption.  Therefore, use an explicit check rather than relying
+	 * on palloc() to complain.
+	 */
+	if (key_count > MaxAllocSize / sizeof(Pairs))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+			  errmsg("number of pairs (%d) exceeds the maximum allowed (%d)",
+					 key_count, (int) (MaxAllocSize / sizeof(Pairs)))));
+
 	key_pairs = palloc(sizeof(Pairs) * key_count);
 
 	for (i = 0, j = 0; i < key_count; i++)
@@ -649,6 +663,7 @@ hstore_slice_to_hstore(PG_FUNCTION_ARGS)
 		PG_RETURN_POINTER(out);
 	}
 
+	/* hstoreArrayToPairs() checked overflow */
 	out_pairs = palloc(sizeof(Pairs) * nkeys);
 	bufsiz = 0;
 
diff --git a/contrib/intarray/_int.h b/contrib/intarray/_int.h
index 11c069890ea..755cd9e097e 100644
--- a/contrib/intarray/_int.h
+++ b/contrib/intarray/_int.h
@@ -5,6 +5,7 @@
 #define ___INT_H__
 
 #include "utils/array.h"
+#include "utils/memutils.h"
 
 /* number ranges for compression */
 #define MAXNUMRANGE 100
@@ -137,6 +138,7 @@ typedef struct QUERYTYPE
 
 #define HDRSIZEQT	offsetof(QUERYTYPE, items)
 #define COMPUTESIZE(size)	( HDRSIZEQT + (size) * sizeof(ITEM) )
+#define QUERYTYPEMAXITEMS	((MaxAllocSize - HDRSIZEQT) / sizeof(ITEM))
 #define GETQUERY(x)  ( (x)->items )
 
 /* "type" codes for ITEM */
diff --git a/contrib/intarray/_int_bool.c b/contrib/intarray/_int_bool.c
index 4e63f6d66c1..62294d1caba 100644
--- a/contrib/intarray/_int_bool.c
+++ b/contrib/intarray/_int_bool.c
@@ -451,6 +451,9 @@ boolop(PG_FUNCTION_ARGS)
 static void
 findoprnd(ITEM *ptr, int4 *pos)
 {
+	/* since this function recurses, it could be driven to stack overflow. */
+	check_stack_depth();
+
 #ifdef BS_DEBUG
 	elog(DEBUG3, (ptr[*pos].type == OPR) ?
 		 "%d  %c" : "%d  %d", *pos, ptr[*pos].val);
@@ -511,7 +514,13 @@ bqarr_in(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("empty query")));
 
+	if (state.num > QUERYTYPEMAXITEMS)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+		errmsg("number of query items (%d) exceeds the maximum allowed (%d)",
+			   state.num, (int) QUERYTYPEMAXITEMS)));
 	commonlen = COMPUTESIZE(state.num);
+
 	query = (QUERYTYPE *) palloc(commonlen);
 	SET_VARSIZE(query, commonlen);
 	query->size = state.num;
diff --git a/contrib/ltree/ltree.h b/contrib/ltree/ltree.h
index 8e4ea4c1513..02c96d6ed78 100644
--- a/contrib/ltree/ltree.h
+++ b/contrib/ltree/ltree.h
@@ -6,6 +6,7 @@
 #include "postgres.h"
 #include "fmgr.h"
 #include "tsearch/ts_locale.h"
+#include "utils/memutils.h"
 
 typedef struct
 {
@@ -112,6 +113,8 @@ typedef struct
 
 #define HDRSIZEQT		MAXALIGN(VARHDRSZ + sizeof(int4))
 #define COMPUTESIZE(size,lenofoperand)	( HDRSIZEQT + (size) * sizeof(ITEM) + (lenofoperand) )
+#define LTXTQUERY_TOO_BIG(size,lenofoperand) \
+	((size) > (MaxAllocSize - HDRSIZEQT - (lenofoperand)) / sizeof(ITEM))
 #define GETQUERY(x)  (ITEM*)( (char*)(x)+HDRSIZEQT )
 #define GETOPERAND(x)	( (char*)GETQUERY(x) + ((ltxtquery*)x)->size * sizeof(ITEM) )
 
diff --git a/contrib/ltree/ltree_io.c b/contrib/ltree/ltree_io.c
index 3e88b81c16e..d64debb5f49 100644
--- a/contrib/ltree/ltree_io.c
+++ b/contrib/ltree/ltree_io.c
@@ -8,6 +8,7 @@
 #include <ctype.h>
 
 #include "ltree.h"
+#include "utils/memutils.h"
 #include "crc32.h"
 
 PG_FUNCTION_INFO_V1(ltree_in);
@@ -64,6 +65,11 @@ ltree_in(PG_FUNCTION_ARGS)
 		ptr += charlen;
 	}
 
+	if (num + 1 > MaxAllocSize / sizeof(nodeitem))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+			 errmsg("number of levels (%d) exceeds the maximum allowed (%d)",
+					num + 1, (int) (MaxAllocSize / sizeof(nodeitem)))));
 	list = lptr = (nodeitem *) palloc(sizeof(nodeitem) * (num + 1));
 	ptr = buf;
 	while (*ptr)
@@ -228,6 +234,11 @@ lquery_in(PG_FUNCTION_ARGS)
 	}
 
 	num++;
+	if (num > MaxAllocSize / ITEMSIZE)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+			 errmsg("number of levels (%d) exceeds the maximum allowed (%d)",
+					num, (int) (MaxAllocSize / ITEMSIZE))));
 	curqlevel = tmpql = (lquery_level *) palloc0(ITEMSIZE * num);
 	ptr = buf;
 	while (*ptr)
diff --git a/contrib/ltree/ltxtquery_io.c b/contrib/ltree/ltxtquery_io.c
index 826f4e1c9dd..13ea58df3f5 100644
--- a/contrib/ltree/ltxtquery_io.c
+++ b/contrib/ltree/ltxtquery_io.c
@@ -9,6 +9,7 @@
 
 #include "crc32.h"
 #include "ltree.h"
+#include "miscadmin.h"
 
 PG_FUNCTION_INFO_V1(ltxtq_in);
 Datum		ltxtq_in(PG_FUNCTION_ARGS);
@@ -213,6 +214,9 @@ makepol(QPRS_STATE *state)
 	int4		lenstack = 0;
 	uint16		flag = 0;
 
+	/* since this function recurses, it could be driven to stack overflow */
+	check_stack_depth();
+
 	while ((type = gettoken_query(state, &val, &lenval, &strval, &flag)) != END)
 	{
 		switch (type)
@@ -277,6 +281,9 @@ makepol(QPRS_STATE *state)
 static void
 findoprnd(ITEM *ptr, int4 *pos)
 {
+	/* since this function recurses, it could be driven to stack overflow. */
+	check_stack_depth();
+
 	if (ptr[*pos].type == VAL || ptr[*pos].type == VALTRUE)
 	{
 		ptr[*pos].left = 0;
@@ -341,8 +348,12 @@ queryin(char *buf)
 				 errmsg("syntax error"),
 				 errdetail("Empty query.")));
 
-	/* make finish struct */
+	if (LTXTQUERY_TOO_BIG(state.num, state.sumlen))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("ltxtquery is too large")));
 	commonlen = COMPUTESIZE(state.num, state.sumlen);
+
 	query = (ltxtquery *) palloc(commonlen);
 	SET_VARSIZE(query, commonlen);
 	query->size = state.num;
diff --git a/src/backend/utils/adt/geo_ops.c b/src/backend/utils/adt/geo_ops.c
index 2cf2f644117..ca03947bc83 100644
--- a/src/backend/utils/adt/geo_ops.c
+++ b/src/backend/utils/adt/geo_ops.c
@@ -1403,6 +1403,7 @@ path_in(PG_FUNCTION_ARGS)
 	char	   *s;
 	int			npts;
 	int			size;
+	int			base_size;
 	int			depth = 0;
 
 	if ((npts = pair_count(str, ',')) <= 0)
@@ -1421,7 +1422,15 @@ path_in(PG_FUNCTION_ARGS)
 		depth++;
 	}
 
-	size = offsetof(PATH, p[0]) +sizeof(path->p[0]) * npts;
+	base_size = sizeof(path->p[0]) * npts;
+	size = offsetof(PATH, p[0]) + base_size;
+
+	/* Check for integer overflow */
+	if (base_size / npts != sizeof(path->p[0]) || size <= base_size)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("too many points requested")));
+
 	path = (PATH *) palloc(size);
 
 	SET_VARSIZE(path, size);
@@ -3465,6 +3474,7 @@ poly_in(PG_FUNCTION_ARGS)
 	POLYGON    *poly;
 	int			npts;
 	int			size;
+	int			base_size;
 	int			isopen;
 	char	   *s;
 
@@ -3473,7 +3483,15 @@ poly_in(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
 			  errmsg("invalid input syntax for type polygon: \"%s\"", str)));
 
-	size = offsetof(POLYGON, p[0]) +sizeof(poly->p[0]) * npts;
+	base_size = sizeof(poly->p[0]) * npts;
+	size = offsetof(POLYGON, p[0]) + base_size;
+
+	/* Check for integer overflow */
+	if (base_size / npts != sizeof(poly->p[0]) || size <= base_size)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("too many points requested")));
+
 	poly = (POLYGON *) palloc0(size);	/* zero any holes */
 
 	SET_VARSIZE(poly, size);
@@ -4379,6 +4397,10 @@ path_poly(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("open path cannot be converted to polygon")));
 
+	/*
+	 * Never overflows: the old size fit in MaxAllocSize, and the new size is
+	 * just a small constant larger.
+	 */
 	size = offsetof(POLYGON, p[0]) +sizeof(poly->p[0]) * path->npts;
 	poly = (POLYGON *) palloc(size);
 
@@ -4484,6 +4506,10 @@ poly_path(PG_FUNCTION_ARGS)
 	int			size;
 	int			i;
 
+	/*
+	 * Never overflows: the old size fit in MaxAllocSize, and the new size is
+	 * smaller by a small constant.
+	 */
 	size = offsetof(PATH, p[0]) +sizeof(path->p[0]) * poly->npts;
 	path = (PATH *) palloc(size);
 
diff --git a/src/backend/utils/adt/tsquery.c b/src/backend/utils/adt/tsquery.c
index 5baa02b1c03..625421545c4 100644
--- a/src/backend/utils/adt/tsquery.c
+++ b/src/backend/utils/adt/tsquery.c
@@ -517,8 +517,13 @@ parse_tsquery(char *buf,
 		return query;
 	}
 
-	/* Pack the QueryItems in the final TSQuery struct to return to caller */
+	if (TSQUERY_TOO_BIG(list_length(state.polstr), state.sumlen))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("tsquery is too large")));
 	commonlen = COMPUTESIZE(list_length(state.polstr), state.sumlen);
+
+	/* Pack the QueryItems in the final TSQuery struct to return to caller */
 	query = (TSQuery) palloc0(commonlen);
 	SET_VARSIZE(query, commonlen);
 	query->size = list_length(state.polstr);
diff --git a/src/backend/utils/adt/tsquery_util.c b/src/backend/utils/adt/tsquery_util.c
index 53093f1e864..08411b0ade0 100644
--- a/src/backend/utils/adt/tsquery_util.c
+++ b/src/backend/utils/adt/tsquery_util.c
@@ -334,6 +334,11 @@ QTN2QT(QTNode *in)
 	QTN2QTState state;
 
 	cntsize(in, &sumlen, &nnode);
+
+	if (TSQUERY_TOO_BIG(nnode, sumlen))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("tsquery is too large")));
 	len = COMPUTESIZE(nnode, sumlen);
 
 	out = (TSQuery) palloc0(len);
diff --git a/src/backend/utils/adt/txid.c b/src/backend/utils/adt/txid.c
index 2907306e928..31867c4fa85 100644
--- a/src/backend/utils/adt/txid.c
+++ b/src/backend/utils/adt/txid.c
@@ -27,6 +27,7 @@
 #include "miscadmin.h"
 #include "libpq/pqformat.h"
 #include "utils/builtins.h"
+#include "utils/memutils.h"
 #include "utils/snapmgr.h"
 
 
@@ -66,6 +67,8 @@ typedef struct
 
 #define TXID_SNAPSHOT_SIZE(nxip) \
 	(offsetof(TxidSnapshot, xip) + sizeof(txid) * (nxip))
+#define TXID_SNAPSHOT_MAX_NXIP \
+	((MaxAllocSize - offsetof(TxidSnapshot, xip)) / sizeof(txid))
 
 /*
  * Epoch values from xact.c
@@ -444,20 +447,12 @@ txid_snapshot_recv(PG_FUNCTION_ARGS)
 	txid		last = 0;
 	int			nxip;
 	int			i;
-	int			avail;
-	int			expect;
 	txid		xmin,
 				xmax;
 
-	/*
-	 * load nxip and check for nonsense.
-	 *
-	 * (nxip > avail) check is against int overflows in 'expect'.
-	 */
+	/* load and validate nxip */
 	nxip = pq_getmsgint(buf, 4);
-	avail = buf->len - buf->cursor;
-	expect = 8 + 8 + nxip * 8;
-	if (nxip < 0 || nxip > avail || expect > avail)
+	if (nxip < 0 || nxip > TXID_SNAPSHOT_MAX_NXIP)
 		goto bad_format;
 
 	xmin = pq_getmsgint64(buf);
diff --git a/src/backend/utils/adt/varbit.c b/src/backend/utils/adt/varbit.c
index 3fa81175fd8..1727f25679e 100644
--- a/src/backend/utils/adt/varbit.c
+++ b/src/backend/utils/adt/varbit.c
@@ -147,12 +147,22 @@ bit_in(PG_FUNCTION_ARGS)
 		sp = input_string;
 	}
 
+	/*
+	 * Determine bitlength from input string.  MaxAllocSize ensures a regular
+	 * input is small enough, but we must check hex input.
+	 */
 	slen = strlen(sp);
-	/* Determine bitlength from input string */
 	if (bit_not_hex)
 		bitlen = slen;
 	else
+	{
+		if (slen > VARBITMAXLEN / 4)
+			ereport(ERROR,
+					(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("bit string length exceeds the maximum allowed (%d)",
+						VARBITMAXLEN)));
 		bitlen = slen * 4;
+	}
 
 	/*
 	 * Sometimes atttypmod is not supplied. If it is supplied we need to make
@@ -449,12 +459,22 @@ varbit_in(PG_FUNCTION_ARGS)
 		sp = input_string;
 	}
 
+	/*
+	 * Determine bitlength from input string.  MaxAllocSize ensures a regular
+	 * input is small enough, but we must check hex input.
+	 */
 	slen = strlen(sp);
-	/* Determine bitlength from input string */
 	if (bit_not_hex)
 		bitlen = slen;
 	else
+	{
+		if (slen > VARBITMAXLEN / 4)
+			ereport(ERROR,
+					(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("bit string length exceeds the maximum allowed (%d)",
+						VARBITMAXLEN)));
 		bitlen = slen * 4;
+	}
 
 	/*
 	 * Sometimes atttypmod is not supplied. If it is supplied we need to make
@@ -534,6 +554,9 @@ varbit_in(PG_FUNCTION_ARGS)
 /*
  * varbit_out -
  *	  Prints the string as bits to preserve length accurately
+ *
+ * XXX varbit_recv() and hex input to varbit_in() can load a value that this
+ * cannot emit.  Consider using hex output for such values.
  */
 Datum
 varbit_out(PG_FUNCTION_ARGS)
@@ -910,6 +933,11 @@ bit_catenate(VarBit *arg1, VarBit *arg2)
 	bitlen1 = VARBITLEN(arg1);
 	bitlen2 = VARBITLEN(arg2);
 
+	if (bitlen1 > VARBITMAXLEN - bitlen2)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("bit string length exceeds the maximum allowed (%d)",
+						VARBITMAXLEN)));
 	bytelen = VARBITTOTALLEN(bitlen1 + bitlen2);
 
 	result = (VarBit *) palloc(bytelen);
diff --git a/src/include/tsearch/ts_type.h b/src/include/tsearch/ts_type.h
index 6a33f851a32..3aa81fd2ff5 100644
--- a/src/include/tsearch/ts_type.h
+++ b/src/include/tsearch/ts_type.h
@@ -13,6 +13,7 @@
 #define _PG_TSTYPE_H_
 
 #include "fmgr.h"
+#include "utils/memutils.h"
 #include "utils/pg_crc.h"
 
 
@@ -242,6 +243,8 @@ typedef TSQueryData *TSQuery;
  * QueryItems, and lenofoperand is the total length of all operands
  */
 #define COMPUTESIZE(size, lenofoperand) ( HDRSIZETQ + (size) * sizeof(QueryItem) + (lenofoperand) )
+#define TSQUERY_TOO_BIG(size, lenofoperand) \
+	((size) > (MaxAllocSize - HDRSIZETQ - (lenofoperand)) / sizeof(QueryItem))
 
 /* Returns a pointer to the first QueryItem in a TSQuery */
 #define GETQUERY(x)  ((QueryItem*)( (char*)(x)+HDRSIZETQ ))
diff --git a/src/include/utils/varbit.h b/src/include/utils/varbit.h
index e329d52e247..58727c66b9a 100644
--- a/src/include/utils/varbit.h
+++ b/src/include/utils/varbit.h
@@ -15,6 +15,8 @@
 #ifndef VARBIT_H
 #define VARBIT_H
 
+#include <limits.h>
+
 #include "fmgr.h"
 
 /*
@@ -53,6 +55,11 @@ typedef struct
 /* Number of bytes needed to store a bit string of a given length */
 #define VARBITTOTALLEN(BITLEN)	(((BITLEN) + BITS_PER_BYTE-1)/BITS_PER_BYTE + \
 								 VARHDRSZ + VARBITHDRSZ)
+/*
+ * Maximum number of bits.  Several code sites assume no overflow from
+ * computing bitlen + X; VARBITTOTALLEN() has the largest such X.
+ */
+#define VARBITMAXLEN		(INT_MAX - BITS_PER_BYTE + 1)
 /* pointer beyond the end of the bit string (like end() in STL containers) */
 #define VARBITEND(PTR)		(((bits8 *) (PTR)) + VARSIZE(PTR))
 /* Mask that will cover exactly one byte, i.e. BITS_PER_BYTE bits */