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Fix unsafe order of operations in foreign-table DDL commands. 

When updating or deleting a system catalog tuple, it's necessary to acquire
RowExclusiveLock on the catalog before looking up the tuple; otherwise a
concurrent VACUUM FULL on the catalog might move the tuple to a different
TID before we can apply the update.  Coding patterns that find the tuple
via a table scan aren't at risk here, but when obtaining the tuple from a
catalog cache, correct ordering is important; and several routines in
foreigncmds.c got it wrong.  Noted while running the regression tests in
parallel with VACUUM FULL of assorted system catalogs.

For consistency I moved all the heap_open calls to the starts of their
functions, including a couple for which there was no actual bug.

Back-patch to 8.4 where foreigncmds.c was added.
This commit is contained in:
Tom Lane 2011-08-14 15:40:21 -04:00
parent 85612039b9
commit 52994e9e56
1 changed files with 18 additions and 21 deletions
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39
src/backend/commands/foreigncmds.c
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@ -215,6 +215,8 @@ AlterForeignDataWrapperOwner(const char *name, Oid newOwnerId)
Oid fdwId;
Form_pg_foreign_data_wrapper form;
rel = heap_open(ForeignDataWrapperRelationId, RowExclusiveLock);
/* Must be a superuser to change a FDW owner */
if (!superuser())
ereport(ERROR,
@ -231,8 +233,6 @@ AlterForeignDataWrapperOwner(const char *name, Oid newOwnerId)
name),
errhint("The owner of a foreign-data wrapper must be a superuser.")));
rel = heap_open(ForeignDataWrapperRelationId, RowExclusiveLock);
tup = SearchSysCacheCopy1(FOREIGNDATAWRAPPERNAME, CStringGetDatum(name));
if (!HeapTupleIsValid(tup))
@ -432,6 +432,8 @@ CreateForeignDataWrapper(CreateFdwStmt *stmt)
ObjectAddress myself;
ObjectAddress referenced;
rel = heap_open(ForeignDataWrapperRelationId, RowExclusiveLock);
/* Must be super user */
if (!superuser())
ereport(ERROR,
@ -455,8 +457,6 @@ CreateForeignDataWrapper(CreateFdwStmt *stmt)
/*
* Insert tuple into pg_foreign_data_wrapper.
*/
rel = heap_open(ForeignDataWrapperRelationId, RowExclusiveLock);
memset(values, 0, sizeof(values));
memset(nulls, false, sizeof(nulls));
@ -545,6 +545,8 @@ AlterForeignDataWrapper(AlterFdwStmt *stmt)
Oid fdwhandler;
Oid fdwvalidator;
rel = heap_open(ForeignDataWrapperRelationId, RowExclusiveLock);
/* Must be super user */
if (!superuser())
ereport(ERROR,
@ -635,9 +637,6 @@ AlterForeignDataWrapper(AlterFdwStmt *stmt)
}
/* Everything looks good - update the tuple */
rel = heap_open(ForeignDataWrapperRelationId, RowExclusiveLock);
tp = heap_modify_tuple(tp, RelationGetDescr(rel),
repl_val, repl_null, repl_repl);
@ -773,6 +772,8 @@ CreateForeignServer(CreateForeignServerStmt *stmt)
ObjectAddress referenced;
ForeignDataWrapper *fdw;
rel = heap_open(ForeignServerRelationId, RowExclusiveLock);
/* For now the owner cannot be specified on create. Use effective user ID. */
ownerId = GetUserId();
@ -798,8 +799,6 @@ CreateForeignServer(CreateForeignServerStmt *stmt)
/*
* Insert tuple into pg_foreign_server.
*/
rel = heap_open(ForeignServerRelationId, RowExclusiveLock);
memset(values, 0, sizeof(values));
memset(nulls, false, sizeof(nulls));
@ -880,6 +879,8 @@ AlterForeignServer(AlterForeignServerStmt *stmt)
Oid srvId;
Form_pg_foreign_server srvForm;
rel = heap_open(ForeignServerRelationId, RowExclusiveLock);
tp = SearchSysCacheCopy1(FOREIGNSERVERNAME,
CStringGetDatum(stmt->servername));
@ -945,9 +946,6 @@ AlterForeignServer(AlterForeignServerStmt *stmt)
}
/* Everything looks good - update the tuple */
rel = heap_open(ForeignServerRelationId, RowExclusiveLock);
tp = heap_modify_tuple(tp, RelationGetDescr(rel),
repl_val, repl_null, repl_repl);
@ -1068,6 +1066,8 @@ CreateUserMapping(CreateUserMappingStmt *stmt)
ForeignServer *srv;
ForeignDataWrapper *fdw;
rel = heap_open(UserMappingRelationId, RowExclusiveLock);
useId = GetUserOidFromMapping(stmt->username, false);
/* Check that the server exists. */
@ -1093,8 +1093,6 @@ CreateUserMapping(CreateUserMappingStmt *stmt)
/*
* Insert tuple into pg_user_mapping.
*/
rel = heap_open(UserMappingRelationId, RowExclusiveLock);
memset(values, 0, sizeof(values));
memset(nulls, false, sizeof(nulls));
@ -1161,6 +1159,8 @@ AlterUserMapping(AlterUserMappingStmt *stmt)
Oid umId;
ForeignServer *srv;
rel = heap_open(UserMappingRelationId, RowExclusiveLock);
useId = GetUserOidFromMapping(stmt->username, false);
srv = GetForeignServerByName(stmt->servername, false);
@ -1218,9 +1218,6 @@ AlterUserMapping(AlterUserMappingStmt *stmt)
}
/* Everything looks good - update the tuple */
rel = heap_open(UserMappingRelationId, RowExclusiveLock);
tp = heap_modify_tuple(tp, RelationGetDescr(rel),
repl_val, repl_null, repl_repl);
@ -1344,11 +1341,13 @@ CreateForeignTable(CreateForeignTableStmt *stmt, Oid relid)
ForeignServer *server;
/*
* Advance command counter to ensure the pg_attribute tuple visible; the
* tuple might be updated to add constraints in previous step.
* Advance command counter to ensure the pg_attribute tuple is visible;
* the tuple might be updated to add constraints in previous step.
*/
CommandCounterIncrement();
ftrel = heap_open(ForeignTableRelationId, RowExclusiveLock);
/*
* For now the owner cannot be specified on create. Use effective user ID.
*/
@ -1368,8 +1367,6 @@ CreateForeignTable(CreateForeignTableStmt *stmt, Oid relid)
/*
* Insert tuple into pg_foreign_table.
*/
ftrel = heap_open(ForeignTableRelationId, RowExclusiveLock);
memset(values, 0, sizeof(values));
memset(nulls, false, sizeof(nulls));