https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=26dafb54e385981ecb13991b6ab660ee86e5c82c
commit 26dafb54e385981ecb13991b6ab660ee86e5c82c
Author: Takashi Yano <takashi.y...@nifty.ne.jp>
Date: Mon Jul 14 10:40:08 2025 +0900
Cygwin: pty: TCIFLUSH also clears readahead buffer in the master
Previously, TCIFLUSH flushed the pipe to_slave which transfers
input from master to slave. However, this was not sufficiant.
The master side holds input data before accept_input() in the
read-ahead buffer. So, if input data before 'enter' key can be
leaked into slave input after TCIFLUSH.
With this patch, TCIFLUSH requests master to flush read-ahead
buffer via master control pipe. To realize this, add cmd filed
to pipe_request structure so that the flush request can be
distinguished from existing pipe handle request.
Addresses: https://cygwin.com/pipermail/cygwin/2025-July/258442.html
Fixes: 41946df6111b (" (fhandler_tty_slave::tcflush): Implement input queue
flushing by calling read with NULL buffer.")
Reported-by: Christoph Reiter <reiter.christ...@gmail.com>
Signed-off-by: Takashi Yano <takashi.y...@nifty.ne.jp>
(cherry picked from commit 2aa41b516055ea9383508342706288deb3baf1f6)
Diff:
---
winsup/cygwin/fhandler/pty.cc | 31 ++++++++++++++++++++++++++-----
winsup/cygwin/local_includes/fhandler.h | 1 +
winsup/cygwin/release/3.6.4 | 3 +++
3 files changed, 30 insertions(+), 5 deletions(-)
diff --git a/winsup/cygwin/fhandler/pty.cc b/winsup/cygwin/fhandler/pty.cc
index 3128b92da..36fddbbe9 100644
--- a/winsup/cygwin/fhandler/pty.cc
+++ b/winsup/cygwin/fhandler/pty.cc
@@ -42,7 +42,14 @@ extern "C" int sscanf (const char *, const char *, ...);
} while (0)
/* pty master control pipe messages */
+enum pipe_request_cmd {
+ GET_HANDLES,
+ FLUSH_INPUT,
+ QUIT
+};
+
struct pipe_request {
+ pipe_request_cmd cmd;
DWORD pid;
};
@@ -871,7 +878,7 @@ fhandler_pty_slave::open (int flags, mode_t)
}
else
{
- pipe_request req = { GetCurrentProcessId () };
+ pipe_request req = { GET_HANDLES, GetCurrentProcessId () };
pipe_reply repl;
DWORD len;
@@ -1139,7 +1146,7 @@ fhandler_pty_slave::reset_switch_to_nat_pipe (void)
__small_sprintf (pipe,
"\\\\.\\pipe\\cygwin-%S-pty%d-master-ctl",
&cygheap->installation_key, get_minor ());
- pipe_request req = { GetCurrentProcessId () };
+ pipe_request req = { GET_HANDLES, GetCurrentProcessId ()
};
pipe_reply repl;
DWORD len;
if (!CallNamedPipe (pipe, &req, sizeof req,
@@ -1597,6 +1604,14 @@ fhandler_pty_slave::tcflush (int queue)
if (queue == TCIFLUSH || queue == TCIOFLUSH)
{
+ char pipe[MAX_PATH];
+ __small_sprintf (pipe,
+ "\\\\.\\pipe\\cygwin-%S-pty%d-master-ctl",
+ &cygheap->installation_key, get_minor ());
+ pipe_request req = { FLUSH_INPUT, GetCurrentProcessId () };
+ pipe_reply repl;
+ DWORD n;
+ CallNamedPipe (pipe, &req, sizeof req, &repl, sizeof repl, &n, 500);
size_t len = UINT_MAX;
read (NULL, len);
ret = ((int) len) >= 0 ? 0 : -1;
@@ -2020,7 +2035,7 @@ fhandler_pty_master::close (int flag)
if (master_ctl && get_ttyp ()->master_pid == myself->pid)
{
char buf[MAX_PATH];
- pipe_request req = { (DWORD) -1 };
+ pipe_request req = { QUIT, GetCurrentProcessId () };
pipe_reply repl;
DWORD len;
@@ -2521,13 +2536,18 @@ fhandler_pty_master::pty_master_thread (const
master_thread_param_t *p)
termios_printf ("RevertToSelf, %E");
goto reply;
}
- if (req.pid == (DWORD) -1) /* Request to finish thread. */
+ if (req.cmd == QUIT) /* Request to finish thread. */
{
/* Check if the requesting process is the master process itself. */
if (pid == GetCurrentProcessId ())
exit = true;
goto reply;
}
+ if (req.cmd == FLUSH_INPUT)
+ {
+ p->master->eat_readahead (-1);
+ goto reply;
+ }
if (NT_SUCCESS (allow))
{
client = OpenProcess (PROCESS_DUP_HANDLE, FALSE, pid);
@@ -3780,6 +3800,7 @@ fhandler_pty_master::get_master_thread_param
(master_thread_param_t *p)
p->to_slave = get_output_handle ();
p->master_ctl = master_ctl;
p->input_available_event = input_available_event;
+ p->master = this;
SetEvent (thread_param_copied_event);
}
@@ -3821,7 +3842,7 @@ fhandler_pty_slave::transfer_input (tty::xfer_dir dir,
HANDLE from, tty *ttyp,
__small_sprintf (pipe,
"\\\\.\\pipe\\cygwin-%S-pty%d-master-ctl",
&cygheap->installation_key, ttyp->get_minor ());
- pipe_request req = { GetCurrentProcessId () };
+ pipe_request req = { GET_HANDLES, GetCurrentProcessId () };
pipe_reply repl;
DWORD len;
if (!CallNamedPipe (pipe, &req, sizeof req,
diff --git a/winsup/cygwin/local_includes/fhandler.h
b/winsup/cygwin/local_includes/fhandler.h
index 3639a92a8..94f4bc552 100644
--- a/winsup/cygwin/local_includes/fhandler.h
+++ b/winsup/cygwin/local_includes/fhandler.h
@@ -2539,6 +2539,7 @@ public:
HANDLE to_slave;
HANDLE master_ctl;
HANDLE input_available_event;
+ fhandler_pty_master *master;
};
/* Parameter set for the static function pty_master_fwd_thread() */
struct master_fwd_thread_param_t {
diff --git a/winsup/cygwin/release/3.6.4 b/winsup/cygwin/release/3.6.4
index 4338214a6..fbc61c811 100644
--- a/winsup/cygwin/release/3.6.4
+++ b/winsup/cygwin/release/3.6.4
@@ -28,3 +28,6 @@ Fixes:
- Fix ACL operations on directories.
Addresses: https://cygwin.com/pipermail/cygwin/2025-July/258433.html
+
+- Make TCIFLUSH also flush read-ahead data in the master.
+ Addresses: https://cygwin.com/pipermail/cygwin/2025-July/258442.html
