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>
diff --git a/src/testdir/test_crash.vim b/src/testdir/test_crash.vim
index a1da68e..5c83e3a 100644
--- a/src/testdir/test_crash.vim
+++ b/src/testdir/test_crash.vim
@@ -66,6 +66,12 @@
\ ' && 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 @@
\ 'crash 5: [OK]',
\ 'crash 6: [OK]',
\ 'crash 7: [OK]',
+ \ 'crash 8: [OK]',
\ ]
call assert_equal(expected, getline(1, '$'))