757c5182f2
1. Integer overflow in internal_size could result in memory corruption in decompression since a zero-length array would be allocated and then written to. This leads to crashes or corruption when traversing an index which has been populated with sufficiently sparse values. Fix by using int64 for computations and checking for overflow. 2. Integer overflow in g_int_compress could cause pessimal merge choices, resulting in unnecessarily large ranges (which would in turn trigger issue 1 above). Fix by using int64 again. 3. Even without overflow, array sizes could become large enough to cause unexplained memory allocation errors. Fix by capping the sizes to a safe limit and report actual errors pointing at gist__intbig_ops as needed. 4. Large inputs to the compression function always consist of large runs of consecutive integers, and the compression loop was processing these one at a time in an O(N^2) manner with a lot of overhead. The expected runtime of this function could easily exceed 6 months for a single call as a result. Fix by performing a linear-time first pass, which reduces the worst case to something on the order of seconds. Backpatch all the way, since this has been wrong forever. Per bug #15518 from report from irc user "dymk", analysis and patch by me. Discussion: https://postgr.es/m/15518-799e426c3b4f8358@postgresql.org |
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README
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/.