b9aa4166fa
smgrDoPendingSyncs had two distinct risks of integer overflow while deciding which way to ensure durability of a newly-created relation. First, it accumulated the total size of all forks in a variable of type BlockNumber (uint32). While we restrict an individual fork's size to fit in that, I don't believe there's such a restriction on all of them added together. Second, it proceeded to multiply the sum by BLCKSZ, which most certainly could overflow a uint32. (The exact expression is total_blocks * BLCKSZ / 1024. The compiler might choose to optimize that to total_blocks * 8, which is not at quite as much risk of overflow as a literal reading would be, but it's still wrong.) If an overflow did occur it could lead to a poor choice to shove a very large relation into WAL instead of fsync'ing it. This wouldn't be fatal, but it could be inefficient. Change total_blocks to uint64 which should be plenty, and rearrange the comparison calculation to be overflow-safe. I noticed this while looking for ramifications of the proposed change in MAX_KILOBYTES. It's not entirely clear to me why wal_skip_threshold is limited to MAX_KILOBYTES in the first place, but in any case this code is unsafe regardless of the range of wal_skip_threshold. Oversight in c6b92041d which introduced wal_skip_threshold, so back-patch to v13. Discussion: https://postgr.es/m/1a01f0-66ec2d80-3b-68487680@27595217 Backpatch-through: 13
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/.