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ae9aac64a3
As gist__int_ops stands in intarray, it is possible to store GiST entries for leaf pages that can cause corruptions when decompressed. Leaf nodes are stored as decompressed all the time by the compression method, and the decompression method should map with that, retrieving the contents of the page without doing any decompression. However, the code authorized the insertion of leaf page data with a higher number of array items than what can be supported, generating a NOTICE message to inform about this matter (199 for a 8k page, for reference). When calling the decompression method, a decompression would be attempted on this leaf node item but the contents should be retrieved as they are. The NOTICE message generated when dealing with the compression of a leaf page and too many elements in the input array for gist__int_ops has been introduced by 08ee64e, removing the marker stored in the array to track if this is actually a leaf node. However, it also missed the fact that the decompression path should do nothing for a leaf page. Hence, as the code stand, a too-large array would be stored as uncompressed but the decompression path would attempt a decompression rather that retrieving the contents as they are. This leads to various problems. First, even if 08ee64e tried to address that, it is possible to do out-of-bound chunk writes with a large input array, with the backend informing about that with WARNINGs. On decompression, retrieving the stored leaf data would lead to incorrect memory reads, leading to crashes or even worse. Perhaps somebody would be interested in expanding the number of array items that can be handled in a leaf page for this operator in the future, which would require revisiting the choice done in 08ee64e, but based on the lack of reports about this problem since 2005 it does not look so. For now, this commit prevents the insertion of data for leaf pages when using more array items that the code can handle on decompression, switching the NOTICE message to an ERROR. If one wishes to use more array items, gist__intbig_ops is an optional choice. While on it, use ERRCODE_PROGRAM_LIMIT_EXCEEDED as error code when a limit is reached, because that's what the module is facing in such cases. Author: Ankit Kumar Pandey, Alexander Lakhin Reviewed-by: Richard Guo, Michael Paquier Discussion: https://postgr.es/m/796b65c3-57b7-bddf-b0d5-a8afafb8b627@gmail.com Discussion: https://postgr.es/m/17888-f72930e6b5ce8c14@postgresql.org Backpatch-through: 11
The PostgreSQL contrib tree
---------------------------
This subtree contains porting tools, analysis utilities, and plug-in
features that are not part of the core PostgreSQL system, mainly
because they address a limited audience or are too experimental to be
part of the main source tree. This does not preclude their
usefulness.
User documentation for each module appears in the main SGML
documentation.
When building from the source distribution, these modules are not
built automatically, unless you build the "world" target. You can
also build and install them all by running "make all" and "make
install" in this directory; or to build and install just one selected
module, do the same in that module's subdirectory.
Some directories supply new user-defined functions, operators, or
types. To make use of one of these modules, after you have installed
the code you need to register the new SQL objects in the database
system by executing a CREATE EXTENSION command. In a fresh database,
you can simply do
CREATE EXTENSION module_name;
See the PostgreSQL documentation for more information about this
procedure.