From 18b91fbe580e747edf0f7ef8edbec4df07bc7245 Mon Sep 17 00:00:00 2001 From: Takashi Yano via Cygwin-patches Date: Sun, 21 Feb 2021 07:45:16 +0900 Subject: [PATCH] Cygwin: pty: Fix segfault caused when tcflush() is called. - After commit 253352e796ff9ec9a447e5375f5bc3e2b92b5293, mc (midnight commander) crashes with segfault if the shell is bash. This is due to NULL pointer access in read(). This patch fixes the issue. Addresses:: https://cygwin.com/pipermail/cygwin/2021-February/247870.html --- winsup/cygwin/fhandler_tty.cc | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc index d30041af1..3fcaa8277 100644 --- a/winsup/cygwin/fhandler_tty.cc +++ b/winsup/cygwin/fhandler_tty.cc @@ -1474,8 +1474,11 @@ wait_retry: out: termios_printf ("%d = read(%p, %lu)", totalread, ptr, len); len = (size_t) totalread; - bool saw_eol = totalread > 0 && strchr ("\r\n", ptr0[totalread -1]); - mask_switch_to_pcon_in (false, saw_eol); + if (ptr0) + { /* Not tcflush() */ + bool saw_eol = totalread > 0 && strchr ("\r\n", ptr0[totalread -1]); + mask_switch_to_pcon_in (false, saw_eol); + } } int