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Fix out-of-memory error handling in ParameterDescription message processing.

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If libpq ran out of memory while constructing the result set, it would hang,
waiting for more data from the server, which might never arrive. To fix,
distinguish between out-of-memory error and not-enough-data cases, and give
a proper error message back to the client on OOM.

There are still similar issues in handling COPY start messages, but let's
handle that as a separate patch.

Michael Paquier, Amit Kapila and me. Backpatch to all supported versions.
This commit is contained in:
Heikki Linnakangas 2015-12-14 18:19:10 +02:00
parent ccde00b9b9
commit 34d136f92a
1 changed files with 53 additions and 11 deletions
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64
src/interfaces/libpq/fe-protocol3.c
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@ -45,7 +45,7 @@
static void handleSyncLoss(PGconn *conn, char id, int msgLength);
static int getRowDescriptions(PGconn *conn, int msgLength);
static int getParamDescriptions(PGconn *conn);
static int getParamDescriptions(PGconn *conn, int msgLength);
static int getAnotherTuple(PGconn *conn, int msgLength);
static int getParameterStatus(PGconn *conn);
static int getNotify(PGconn *conn);
@ -278,8 +278,17 @@ pqParseInput3(PGconn *conn)
return;
break;
case 'T': /* Row Description */
if (conn->result == NULL ||
conn->queryclass == PGQUERY_DESCRIBE)
if (conn->result != NULL &&
conn->result->resultStatus == PGRES_FATAL_ERROR)
{
/*
* We've already choked for some reason. Just discard
* the data till we get to the end of the query.
*/
conn->inCursor += msgLength;
}
else if (conn->result == NULL ||
conn->queryclass == PGQUERY_DESCRIBE)
{
/* First 'T' in a query sequence */
if (getRowDescriptions(conn, msgLength))
@ -329,9 +338,10 @@ pqParseInput3(PGconn *conn)
}
break;
case 't': /* Parameter Description */
if (getParamDescriptions(conn))
if (getParamDescriptions(conn, msgLength))
return;
break;
/* getParamDescriptions() moves inStart itself */
continue;
case 'D': /* Data Row */
if (conn->result != NULL &&
conn->result->resultStatus == PGRES_TUPLES_OK)
@ -637,20 +647,21 @@ advance_and_error:
* that shouldn't happen often, since 't' messages usually fit in a packet.
*/
static int
getParamDescriptions(PGconn *conn)
getParamDescriptions(PGconn *conn, int msgLength)
{
PGresult *result;
int nparams;
int i;
const char *errmsg = NULL;
result = PQmakeEmptyPGresult(conn, PGRES_COMMAND_OK);
if (!result)
goto failure;
goto advance_and_error;
/* parseInput already read the 't' label and message length. */
/* the next two bytes are the number of parameters */
if (pqGetInt(&(result->numParameters), 2, conn))
goto failure;
goto not_enough_data;
nparams = result->numParameters;
/* allocate space for the parameter descriptors */
@ -659,7 +670,7 @@ getParamDescriptions(PGconn *conn)
result->paramDescs = (PGresParamDesc *)
pqResultAlloc(result, nparams * sizeof(PGresParamDesc), TRUE);
if (!result->paramDescs)
goto failure;
goto advance_and_error;
MemSet(result->paramDescs, 0, nparams * sizeof(PGresParamDesc));
}
@ -669,17 +680,48 @@ getParamDescriptions(PGconn *conn)
int typid;
if (pqGetInt(&typid, 4, conn))
goto failure;
goto not_enough_data;
result->paramDescs[i].typid = typid;
}
/* Success! */
conn->result = result;
/* Advance inStart to show that the "t" message has been processed. */
conn->inStart = conn->inCursor;
return 0;
failure:
not_enough_data:
PQclear(result);
return EOF;
advance_and_error:
/* Discard unsaved result, if any */
if (result && result != conn->result)
PQclear(result);
/* Discard the failed message by pretending we read it */
conn->inStart += 5 + msgLength;
/*
* Replace partially constructed result with an error result. First
* discard the old result to try to win back some memory.
*/
pqClearAsyncResult(conn);
/*
* If preceding code didn't provide an error message, assume "out of
* memory" was meant. The advantage of having this special case is that
* freeing the old result first greatly improves the odds that gettext()
* will succeed in providing a translation.
*/
if (!errmsg)
errmsg = libpq_gettext("out of memory");
printfPQExpBuffer(&conn->errorMessage, "%s\n", errmsg);
pqSaveErrorResult(conn);
return 0;
}
/*