patch 9.0.1969: [security] buffer-overflow in trunc_string() Commit: https://github.com/vim/vim/commit/3bd7fa12e146c6051490d048a4acbfba974eeb04 Author: Christian Brabandt <cb@256bit.org> Date: Mon Oct 2 20:59:08 2023 +0200 patch 9.0.1969: [security] buffer-overflow in trunc_string() Problem: buffer-overflow in trunc_string() Solution: Add NULL at end of buffer Currently trunc_string() assumes that when the string is too long, buf[e-1] will always be writeable. But that assumption may not always be true. The condition currently looks like this else if (e + 3 < buflen) [...] else { // can't fit in the "...", just truncate it buf[e - 1] = NUL; } but this means, we may run into the last else clause with e still being larger than buflen. So a buffer overflow occurs. So instead of using `buf[e - 1]`, let's just always truncate at `buf[buflen - 1]` which should always be writable. Signed-off-by: Christian Brabandt <cb@256bit.org>

--- a/src/testdir/test_crash.vim
+++ b/src/testdir/test_crash.vim
@@ -66,6 +66,12 @@ func Test_crash1()
     \ '  && echo "crash 7: [OK]" >> X_crash1_result.txt' .. "\<cr>")
   call TermWait(buf, 3000)
 
+  let file = 'crash/vim_msg_trunc_poc'
+  let args = printf(cmn_args, vim, file)
+  call term_sendkeys(buf, args ..
+    \ '  || echo "crash 8: [OK]" >> X_crash1_result.txt' .. "\<cr>")
+  call TermWait(buf, 3000)
+
   " clean up
   exe buf .. "bw!"
 
@@ -79,6 +85,7 @@ func Test_crash1()
       \ 'crash 5: [OK]',
       \ 'crash 6: [OK]',
       \ 'crash 7: [OK]',
+      \ 'crash 8: [OK]',
       \ ]
 
   call assert_equal(expected, getline(1, '$'))