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

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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 15:40:41 -04:00
parent ceaf5052c6
commit 3c96f5c647
1 changed files with 14 additions and 17 deletions
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31
src/backend/commands/foreigncmds.c
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@ -202,6 +202,8 @@ 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,
@ -218,8 +220,6 @@ 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 = SearchSysCacheCopy(FOREIGNDATAWRAPPERNAME,
CStringGetDatum(name),
0, 0, 0);
@ -344,6 +344,8 @@ CreateForeignDataWrapper(CreateFdwStmt *stmt)
Datum fdwoptions;
Oid ownerId;
rel = heap_open(ForeignDataWrapperRelationId, RowExclusiveLock);
/* Must be super user */
if (!superuser())
ereport(ERROR,
@ -367,8 +369,6 @@ 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));
@ -439,6 +439,8 @@ AlterForeignDataWrapper(AlterFdwStmt *stmt)
Datum datum;
Oid fdwvalidator;
rel = heap_open(ForeignDataWrapperRelationId, RowExclusiveLock);
/* Must be super user */
if (!superuser())
ereport(ERROR,
@ -518,9 +520,6 @@ 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);
@ -620,6 +619,8 @@ 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();
@ -645,8 +646,6 @@ CreateForeignServer(CreateForeignServerStmt *stmt)
/*
* Insert tuple into pg_foreign_server.
*/
rel = heap_open(ForeignServerRelationId, RowExclusiveLock);
memset(values, 0, sizeof(values));
memset(nulls, false, sizeof(nulls));
@ -721,6 +720,8 @@ AlterForeignServer(AlterForeignServerStmt *stmt)
Oid srvId;
Form_pg_foreign_server srvForm;
rel = heap_open(ForeignServerRelationId, RowExclusiveLock);
tp = SearchSysCacheCopy(FOREIGNSERVERNAME,
CStringGetDatum(stmt->servername),
0, 0, 0);
@ -787,9 +788,6 @@ 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);
@ -911,6 +909,8 @@ CreateUserMapping(CreateUserMappingStmt *stmt)
ForeignServer *srv;
ForeignDataWrapper *fdw;
rel = heap_open(UserMappingRelationId, RowExclusiveLock);
useId = GetUserOidFromMapping(stmt->username, false);
/* Check that the server exists. */
@ -937,8 +937,6 @@ CreateUserMapping(CreateUserMappingStmt *stmt)
/*
* Insert tuple into pg_user_mapping.
*/
rel = heap_open(UserMappingRelationId, RowExclusiveLock);
memset(values, 0, sizeof(values));
memset(nulls, false, sizeof(nulls));
@ -997,6 +995,8 @@ AlterUserMapping(AlterUserMappingStmt *stmt)
Oid umId;
ForeignServer *srv;
rel = heap_open(UserMappingRelationId, RowExclusiveLock);
useId = GetUserOidFromMapping(stmt->username, false);
srv = GetForeignServerByName(stmt->servername, false);
@ -1057,9 +1057,6 @@ 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);