https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=c18369d8f5dbb31be5467ae6d188fd05b864b691
commit c18369d8f5dbb31be5467ae6d188fd05b864b691 Author: Takashi Yano <[email protected]> Date: Sun Feb 22 23:26:43 2026 +0900 Cygwin: pty: Fix handling of data after CSI6n response Previously, CSI6n was not handled correctly if the some sequences are appended after the response for CSI6n. Especially, if the appended sequence is a ESC sequence, which is longer than the expected maximum length of the CSI6n response, the sequence will not be written atomically. Moreover, when the terminal's CSI 6n response and subsequent data (e.g. keystrokes) arrive in the same write buffer, master::write() processes all of it inside the pcon_start loop and returns early. Bytes after the 'R' terminator go through per-byte line_edit() in that loop instead of falling through to the `nat` pipe fast path or the normal bulk `line_edit()` call. Due to this behaviour, the chance of code conversion to the terminal code page for the subsequent data in `to_be_read_from_nat_pipe()` case, will be lost. Fix this by breaking out of the loop when 'R' is found and letting the remaining data fall through to the normal write paths, which are now reachable because `pcon_start` has been cleared. Fixes: f20641789427 ("Cygwin: pty: Reduce unecessary input transfer.") Signed-off-by: Takashi Yano <[email protected]> Co-authored-by: Johannes Schindelin <[email protected]> Reviewed-by: Johannes Schindelin <[email protected]> (cherry picked from commit b4942fffd91cb91ea040bfb2778761cc6663a2b2) Diff: --- winsup/cygwin/fhandler/pty.cc | 42 ++++++++++++++++++++++++------------------ 1 file changed, 24 insertions(+), 18 deletions(-) diff --git a/winsup/cygwin/fhandler/pty.cc b/winsup/cygwin/fhandler/pty.cc index 2da46f8d9..f46c7a86f 100644 --- a/winsup/cygwin/fhandler/pty.cc +++ b/winsup/cygwin/fhandler/pty.cc @@ -2120,6 +2120,8 @@ fhandler_pty_master::close (int flag) ssize_t fhandler_pty_master::write (const void *ptr, size_t len) { + size_t orig_len = len; + ssize_t ret; char *p = (char *) ptr; termios &ti = tc ()->ti; @@ -2143,7 +2145,8 @@ fhandler_pty_master::write (const void *ptr, size_t len) DWORD n; WaitForSingleObject (input_mutex, mutex_timeout); - for (size_t i = 0; i < len; i++) + len = 0; + for (size_t i = 0; i < orig_len; i++) { if (p[i] == '\033') { @@ -2168,18 +2171,21 @@ fhandler_pty_master::write (const void *ptr, size_t len) line_edit (p + i, 1, ti, &ret); if (state == 1 && p[i] == 'R') state = 2; - } - if (state == 2) - { - /* req_xfer_input is true if "ESC[6n" was sent just for - triggering transfer_input() in master. In this case, - the responce sequence should not be written. */ - if (!get_ttyp ()->req_xfer_input) - WriteFile (to_slave_nat, wpbuf, ixput, &n, NULL); - ixput = 0; - state = 0; - get_ttyp ()->req_xfer_input = false; - get_ttyp ()->pcon_start = false; + if (state == 2) + { + /* req_xfer_input is true if "ESC[6n" was sent just for + triggering transfer_input() in master. In this case, + the response sequence should not be written. */ + if (!get_ttyp ()->req_xfer_input) + WriteFile (to_slave_nat, wpbuf, ixput, &n, NULL); + len = orig_len - i - 1; + ptr = p + i + 1; + ixput = 0; + state = 0; + get_ttyp ()->req_xfer_input = false; + get_ttyp ()->pcon_start = false; + break; + } } ReleaseMutex (input_mutex); @@ -2204,8 +2210,8 @@ fhandler_pty_master::write (const void *ptr, size_t len) } get_ttyp ()->pcon_start_pid = 0; } - - return len; + if (len == 0) + return orig_len; } /* Write terminal input to to_slave_nat pipe instead of output_handle @@ -2245,7 +2251,7 @@ fhandler_pty_master::write (const void *ptr, size_t len) WriteFile (to_slave_nat, buf, nlen, &n, NULL); ReleaseMutex (input_mutex); - return len; + return orig_len; } /* The code path reaches here when pseudo console is not activated @@ -2267,8 +2273,8 @@ fhandler_pty_master::write (const void *ptr, size_t len) ReleaseMutex (input_mutex); if (status > line_edit_signalled && status != line_edit_pipe_full) - ret = -1; - return ret; + return -1; + return orig_len - len + ret; } void
