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Commitc77d066

Browse files
committed
Add some code to ensure that we don't lose communication sync due to
an oversize message, per suggestion from Oliver Jowett. I'm a bitdubious that this is a real problem, since the client likely doesn'thave any more space available than the server, but it's not hard tomake it behave according to the protocol intention.
1 parent6e53f18 commitc77d066

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1 file changed

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-5
lines changed

1 file changed

+52
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‎src/backend/libpq/pqcomm.c

Lines changed: 52 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -30,7 +30,7 @@
3030
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
3131
* Portions Copyright (c) 1994, Regents of the University of California
3232
*
33-
*$PostgreSQL: pgsql/src/backend/libpq/pqcomm.c,v 1.172 2004/09/26 00:26:19 tgl Exp $
33+
*$PostgreSQL: pgsql/src/backend/libpq/pqcomm.c,v 1.173 2004/10/18 23:23:19 tgl Exp $
3434
*
3535
*-------------------------------------------------------------------------
3636
*/
@@ -777,6 +777,36 @@ pq_getbytes(char *s, size_t len)
777777
return0;
778778
}
779779

780+
/* --------------------------------
781+
*pq_discardbytes- throw away a known number of bytes
782+
*
783+
*same as pq_getbytes except we do not copy the data to anyplace.
784+
*this is used for resynchronizing after read errors.
785+
*
786+
*returns 0 if OK, EOF if trouble
787+
* --------------------------------
788+
*/
789+
staticint
790+
pq_discardbytes(size_tlen)
791+
{
792+
size_tamount;
793+
794+
while (len>0)
795+
{
796+
while (PqRecvPointer >=PqRecvLength)
797+
{
798+
if (pq_recvbuf())/* If nothing in buffer, then recv some */
799+
returnEOF;/* Failed to recv data */
800+
}
801+
amount=PqRecvLength-PqRecvPointer;
802+
if (amount>len)
803+
amount=len;
804+
PqRecvPointer+=amount;
805+
len-=amount;
806+
}
807+
return0;
808+
}
809+
780810
/* --------------------------------
781811
*pq_getstring- get a null terminated string from connection
782812
*
@@ -867,9 +897,8 @@ pq_getmessage(StringInfo s, int maxlen)
867897
}
868898

869899
len=ntohl(len);
870-
len-=4;/* discount length itself */
871900

872-
if (len<0||
901+
if (len<4||
873902
(maxlen>0&&len>maxlen))
874903
{
875904
ereport(COMMERROR,
@@ -878,10 +907,28 @@ pq_getmessage(StringInfo s, int maxlen)
878907
returnEOF;
879908
}
880909

910+
len-=4;/* discount length itself */
911+
881912
if (len>0)
882913
{
883-
/* Allocate space for message */
884-
enlargeStringInfo(s,len);
914+
/*
915+
* Allocate space for message. If we run out of room (ridiculously
916+
* large message), we will elog(ERROR), but we want to discard the
917+
* message body so as not to lose communication sync.
918+
*/
919+
PG_TRY();
920+
{
921+
enlargeStringInfo(s,len);
922+
}
923+
PG_CATCH();
924+
{
925+
if (pq_discardbytes(len)==EOF)
926+
ereport(COMMERROR,
927+
(errcode(ERRCODE_PROTOCOL_VIOLATION),
928+
errmsg("incomplete message from client")));
929+
PG_RE_THROW();
930+
}
931+
PG_END_TRY();
885932

886933
/* And grab the message */
887934
if (pq_getbytes(s->data,len)==EOF)

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