patch 9.0.2121: [security]: use-after-free in ex_substitute Commit: https://github.com/vim/vim/commit/26c11c56888d01e298cd8044caf860f3c26f57bb Author: Christian Brabandt <cb@256bit.org> Date: Wed Nov 22 21:26:41 2023 +0100 patch 9.0.2121: [security]: use-after-free in ex_substitute Problem: [security]: use-after-free in ex_substitute Solution: always allocate memory closes: #13552 A recursive :substitute command could cause a heap-use-after free in Vim (CVE-2023-48706). The whole reproducible test is a bit tricky, I can only reproduce this reliably when no previous substitution command has been used yet (which is the reason, the test needs to run as first one in the test_substitute.vim file) and as a combination of the `:~` command together with a :s command that contains the special substitution atom `~\=` which will make use of a sub-replace special atom and calls a vim script function. There was a comment in the existing :s code, that already makes the `sub` variable allocate memory so that a recursive :s call won't be able to cause any issues here, so this was known as a potential problem already. But for the current test-case that one does not work, because the substitution does not start with `\=` but with `~\=` (and since there does not yet exist a previous substitution atom, Vim will simply increment the `sub` pointer (which then was not allocated dynamically) and later one happily use a sub-replace special expression (which could then free the `sub` var). The following commit fixes this, by making the sub var always using allocated memory, which also means we need to free the pointer whenever we leave the function. Since sub is now always an allocated variable, we also do no longer need the sub_copy variable anymore, since this one was used to indicated when sub pointed to allocated memory (and had therefore to be freed on exit) and when not. Github Security Advisory: https://github.com/vim/vim/security/advisories/GHSA-c8qm-x72m-q53q Signed-off-by: Christian Brabandt <cb@256bit.org>

Vim		Vi IMproved.  A clone of the UNIX text editor Vi.  Very useful
		for editing programs and other plain ASCII text.  Full Vi
		compatibility and includes all Ex commands.  Extra features
		above Vi: Multilevel undo, multiple windows, syntax
		highlighting, command line history, folding, improved command
		line editing, command typeahead display, command to display
		yank buffers, possibility to edit binary files, file name
		stack, support for Manx QuickFix and other compiler's error
		messages, shows current file name in window title, on-line
		help, rectangular cut/paste, etc., etc., etc...

		Version 9.0.  Also runs under UNIX, MS-Windows, Mac, etc.
		vim90rt.tgz  contains the documentation and syntax files.
		vim90bin.tgz contains the binaries.
		vim90src.tgz contains the sources.
		Author: Bram Moolenaar et al.


Xxd		Hex dumper and reader.  Can be used to view files as hex, edit
		them and write them back.  Can also be used to patch files.

		Version 2022 Jan 14
		Author: Juergen Weigert