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SHMEM_ATTACH_UNKNOWN_SIZE can be passed as argument to ShmemRequestStruct() when the caller wants to attach to an existing shared memory structure whose size it doesn't know. If the shared memory structure doesn't exist, the request should fail, but instead, ProcessShmemRequestsAfterStartup() tried to create the structure with size = -1. That led to integer overflow in ShmemAllocRaw() and memory corruption. Fix by rejecting requests with SHMEM_ATTACH_UNKNOWN_SIZE when the structure doesn't exist. Also add an integer overflow check in ShmemAllocRaw(), to protect from this kind of confusion or simply too large requests. Also document SHMEM_ATTACH_UNKNOWN_SIZE. Author: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> Discussion: https://www.postgresql.org/message-id/CAExHW5u_fTsOAS85kG981Vu6eR1GV-344rup6zYew7xMjEDREw@mail.gmail.com Backpatch-through: 19
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/.