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>

" Test for Vim9 script with failures, causing memory leaks to be reported.
" The leaks happen after a fork() and can be ignored.

source check.vim

def Test_assignment()
  if !has('channel')
    CheckFeature channel
  else
    var chan1: channel
    var job1: job
    var job2: job = job_start('willfail')
  endif
enddef

" Unclear why this test causes valgrind to report problems.
def Test_job_info_return_type()
  if !has('job')
    CheckFeature job
  else
    var job: job = job_start(&shell)
    var jobs = job_info()
    assert_equal('list<job>', typename(jobs))
    assert_equal('dict<any>', typename(job_info(jobs[0])))
    job_stop(job)
  endif
enddef

" Using "idx" from a legacy global function does not work.
" This caused a crash when called from legacy context.
" This creates a dict that contains a partial that refers to the dict, causing
" valgrind to report "possibly leaked memory".
func Test_partial_call_fails()
  let lines =<< trim END
      vim9script

      var l = ['a', 'b', 'c']
      def Iter(container: any): any
        var idx = -1
        var obj = {state: container}
        def g:NextItem__(self: dict<any>): any
          ++idx
          return self.state[idx]
        enddef
        obj.__next__ = function('g:NextItem__', [obj])
        return obj
      enddef

      var it = Iter(l)
      echo it.__next__()
  END
  call writefile(lines, 'XpartialCall', 'D')
  let caught = 'no'
  try
    source XpartialCall
  catch /E1248:/
    let caught = 'yes'
  endtry
  call assert_equal('yes', caught)
  delfunc g:NextItem__
endfunc