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Defend against crash while processing Describe Statement or Describe Portal

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messages, when client attempts to execute these outside a transaction (start
one) or in a failed transaction (reject message, except for COMMIT/ROLLBACK
statements which we can handle).  Per report from Francisco Figueiredo Jr.
This commit is contained in:
Tom Lane
2005-12-14 17:06:28 +00:00
parent 426292663a
commit 4ce6be4f5e
3 changed files with 77 additions and 3 deletions
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51
src/backend/tcop/postgres.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.470 2005/11/22 18:17:21 momjian Exp $
* $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.471 2005/12/14 17:06:27 tgl Exp $
*
* NOTES
* this is the "main" module of the postgres backend and
@ -1849,6 +1849,15 @@ exec_describe_statement_message(const char *stmt_name)
ListCell *l;
StringInfoData buf;
/*
* Start up a transaction command. (Note that this will normally change
* current memory context.) Nothing happens if we are already in one.
*/
start_xact_command();
/* Switch back to message context */
MemoryContextSwitchTo(MessageContext);
/* Find prepared statement */
if (stmt_name[0] != '\0')
pstmt = FetchPreparedStatement(stmt_name, true);
@ -1862,6 +1871,22 @@ exec_describe_statement_message(const char *stmt_name)
errmsg("unnamed prepared statement does not exist")));
}
/*
* If we are in aborted transaction state, we can't safely create a result
* tupledesc, because that needs catalog accesses. Hence, refuse to
* Describe statements that return data. (We shouldn't just refuse all
* Describes, since that might break the ability of some clients to issue
* COMMIT or ROLLBACK commands, if they use code that blindly Describes
* whatever it does.) We can Describe parameters without doing anything
* dangerous, so we don't restrict that.
*/
if (IsAbortedTransactionBlockState() &&
PreparedStatementReturnsTuples(pstmt))
ereport(ERROR,
(errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
errmsg("current transaction is aborted, "
"commands ignored until end of transaction block")));
if (whereToSendOutput != DestRemote)
return; /* can't actually do anything... */
@ -1902,12 +1927,36 @@ exec_describe_portal_message(const char *portal_name)
{
Portal portal;
/*
* Start up a transaction command. (Note that this will normally change
* current memory context.) Nothing happens if we are already in one.
*/
start_xact_command();
/* Switch back to message context */
MemoryContextSwitchTo(MessageContext);
portal = GetPortalByName(portal_name);
if (!PortalIsValid(portal))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_CURSOR),
errmsg("portal \"%s\" does not exist", portal_name)));
/*
* If we are in aborted transaction state, we can't run
* SendRowDescriptionMessage(), because that needs catalog accesses.
* Hence, refuse to Describe portals that return data. (We shouldn't just
* refuse all Describes, since that might break the ability of some
* clients to issue COMMIT or ROLLBACK commands, if they use code that
* blindly Describes whatever it does.)
*/
if (IsAbortedTransactionBlockState() &&
portal->tupDesc)
ereport(ERROR,
(errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
errmsg("current transaction is aborted, "
"commands ignored until end of transaction block")));
if (whereToSendOutput != DestRemote)
return; /* can't actually do anything... */