afd63e0ad2
On the first LockAcquire for a lock tag, LockAcquireExtended() creates a LOCALLOCK entry in the hash table LockMethodLocalHash, with lockOwners set to NULL. lockOwners is then allocated in TopMemoryContext. If the allocation fails, the hash entry would persist with lockOwners still NULL and maxLockOwners already set to 8. A follow-up LockAcquire() on the same entry would crash on a NULL pointer dereference. This commit adds an extra layer of safety for such a case, by re-attempting MemoryContextAlloc() if a LOCALLOCK entry exists but its lockOwners is still NULL due to a previous in-flight allocation failure. This problem is unlikely going to show up in practice, so no backpatch is done. Author: Bryan Green <dbryan.green@gmail.com> Author: Mark Dilger <mark.dilger@enterprisedb.com> Discussion: https://postgr.es/m/c9a5eeb1-4d31-46e1-bb9e-33448a23a5d3@gmail.com
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.