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An extra check for pending bytes in the SSL layer has been part of pqReadReady() for a very long time (79ff2e96d). But when GSS transport encryption was added, it didn't receive the same treatment. (As79ff2e96dnotes, "The bug that I fixed in this patch is exceptionally hard to reproduce reliably.") Without that check, it's possible to hit a hang in gssencmode, if the server splits a large libpq message such that the final message in a streamed response is part of the same wrapped token as the split message: DataRowDataRowDataRowDataRowDataRowData -- token boundary -- RowDataRowCommandCompleteReadyForQuery If the split message takes up enough memory to nearly fill libpq's receive buffer, libpq may return from pqReadData() before the later messages are pulled out of the PqGSSRecvBuffer. Without additional socket activity from the server, pqReadReady() (via pqSocketCheck()) will never again return true, hanging the connection. Pull the pending-bytes check into the pqsecure API layer, where both SSL and GSS now implement it. Note that this does not fix the root problem! Third party clients of libpq have no way to call pqsecure_read_is_pending() in their own polling. This just brings the GSS implementation up to par with the existing SSL workaround; a broader fix is left to a subsequent commit. In preparation for the broader fix, this patch already changes the *_read_pending() functions to return the number of bytes in the buffer rather than just a boolean. The current callers don't need that, but the subsequent fix will. Author: Jacob Champion <jacob.champion@enterprisedb.com> Discussion: https://postgr.es/m/CAOYmi%2BmpymrgZ76Jre2dx_PwRniS9YZojwH0rZnTuiGHCsj0rA%40mail.gmail.com Backpatch-through: 14
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. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download/ See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.