From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2155) id A980A3987C22; Wed, 21 Apr 2021 15:43:45 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org A980A3987C22 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Corinna Vinschen To: cygwin-cvs@sourceware.org Subject: [newlib-cygwin] Cygwin: pty: Additional race issue fix regarding pseudo console. X-Act-Checkin: newlib-cygwin X-Git-Author: Takashi Yano X-Git-Refname: refs/heads/master X-Git-Oldrev: 13fd26ecf5ca8417146d57b45aed0133435c3497 X-Git-Newrev: 01387f1ff41eada228bafacbfb95f49fb8a9aca2 Message-Id: <20210421154345.A980A3987C22@sourceware.org> Date: Wed, 21 Apr 2021 15:43:45 +0000 (GMT) X-BeenThere: cygwin-cvs@cygwin.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Cygwin core component git logs List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Apr 2021 15:43:45 -0000 https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=01387f1ff41eada228bafacbfb95f49fb8a9aca2 commit 01387f1ff41eada228bafacbfb95f49fb8a9aca2 Author: Takashi Yano Date: Wed Apr 21 12:06:00 2021 +0900 Cygwin: pty: Additional race issue fix regarding pseudo console. - In commit bb93c6d7, the race issue was not completely fixed. In the pseudo console inheritance, if the destination process to which the ownership of pseudo console switches, is found but exits before switching, the inheritance fails. Currently, this extremely rarely happens. This patch fixes the issue. Diff: --- winsup/cygwin/fhandler_tty.cc | 47 +++++++++++++------------------------------ 1 file changed, 14 insertions(+), 33 deletions(-) diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc index d44728795..e4480771b 100644 --- a/winsup/cygwin/fhandler_tty.cc +++ b/winsup/cygwin/fhandler_tty.cc @@ -64,6 +64,8 @@ struct pipe_reply { extern HANDLE attach_mutex; /* Defined in fhandler_console.cc */ +inline static bool pcon_pid_alive (DWORD pid); + DWORD fhandler_pty_common::get_console_process_id (DWORD pid, bool match, bool cygwin, bool stub_only) @@ -90,20 +92,18 @@ fhandler_pty_common::get_console_process_id (DWORD pid, bool match, else { pinfo p (cygwin_pid (list[i])); - if (!!p && p->dwProcessId && p->exec_dwProcessId - && p->dwProcessId != p->exec_dwProcessId) + if (!!p && p->exec_dwProcessId) { - res_pri = list[i]; + res_pri = stub_only ? p->exec_dwProcessId : list[i]; break; } - if (!!p && !res) + if (!p && !res && pcon_pid_alive (list[i]) && stub_only) + res = list[i]; + if (!!p && !res && !stub_only) res = list[i]; } } - if (stub_only) - return res_pri; - else - return res_pri ?: res; + return res_pri ?: res; } static bool isHybrid; @@ -3384,35 +3384,17 @@ fallback: void fhandler_pty_slave::close_pseudoconsole (tty *ttyp, DWORD force_switch_to) { - DWORD switch_to_stub = 0, switch_to = 0; - DWORD new_pcon_pid = 0; + DWORD switch_to = 0; if (force_switch_to) { - switch_to_stub = force_switch_to; - new_pcon_pid = force_switch_to; + switch_to = force_switch_to; ttyp->setpgid (force_switch_to + MAX_PID); } else if (pcon_pid_self (ttyp->pcon_pid)) { /* Search another process which attaches to the pseudo console */ DWORD current_pid = myself->exec_dwProcessId ?: myself->dwProcessId; - switch_to = get_console_process_id (current_pid, false, true); - if (switch_to) - { - pinfo p (cygwin_pid (switch_to)); - if (p) - { - if (p->exec_dwProcessId) - switch_to_stub = p->exec_dwProcessId; - new_pcon_pid = p->exec_dwProcessId; - } - } - else - { - switch_to = get_console_process_id (current_pid, false, false); - if (switch_to) - new_pcon_pid = switch_to; - } + switch_to = get_console_process_id (current_pid, false, true, true); } if (ttyp->pcon_activated) { @@ -3420,7 +3402,6 @@ fhandler_pty_slave::close_pseudoconsole (tty *ttyp, DWORD force_switch_to) ttyp->previous_output_code_page = GetConsoleOutputCP (); if (pcon_pid_self (ttyp->pcon_pid)) { - switch_to = switch_to_stub ?: switch_to; if (switch_to) { /* Change pseudo console owner to another process */ @@ -3454,7 +3435,7 @@ fhandler_pty_slave::close_pseudoconsole (tty *ttyp, DWORD force_switch_to) CloseHandle (ttyp->h_pcon_conhost_process); CloseHandle (ttyp->h_pcon_in); CloseHandle (ttyp->h_pcon_out); - ttyp->pcon_pid = new_pcon_pid; + ttyp->pcon_pid = switch_to; ttyp->h_pcon_write_pipe = new_write_pipe; ttyp->h_pcon_condrv_reference = new_condrv_reference; ttyp->h_pcon_conhost_process = new_conhost_process; @@ -3513,8 +3494,8 @@ fhandler_pty_slave::close_pseudoconsole (tty *ttyp, DWORD force_switch_to) } else if (pcon_pid_self (ttyp->pcon_pid)) { - if (switch_to_stub) - ttyp->pcon_pid = new_pcon_pid; + if (switch_to) + ttyp->pcon_pid = switch_to; else { ttyp->pcon_pid = 0;