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From: Takashi Yano <tyan0@sourceware.org> To: cygwin-cvs@sourceware.org Subject: [newlib-cygwin] Cygwin: stat(): Fix "Bad address" error on stat() for /dev/tty. Date: Mon, 10 Jul 2023 08:37:47 +0000 (GMT) [thread overview] Message-ID: <20230710083747.764C23858D35@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=3edb55af820025013b87fdb53249676067a8b8ee commit 3edb55af820025013b87fdb53249676067a8b8ee Author: Takashi Yano <takashi.yano@nifty.ne.jp> Date: Fri Jul 7 06:11:52 2023 +0900 Cygwin: stat(): Fix "Bad address" error on stat() for /dev/tty. As reported in https://cygwin.com/pipermail/cygwin/2023-June/253888.html, "Bad address" error occurs when stat() is called after the commit 3721a756b0d8 ("Cygwin: console: Make the console accessible from other terminals."). There are two problems in the current code. One is fhandler_console:: fstat() calls get_ttyp()->getsid(). However, fh_alloc() in dtable.cc omits to initialize the fhandler_console instance when stat() is called. Due to this, get_ttyp() returns NULL and access violation occurs. The other problem is fh_alloc() assigns fhandler_console even if the CTTY is not a console. So the first problem above occurs even if the CTTY is a pty. This patch fixes the issue by: 1) Call set_unit() to initialize _tc if the get_ttyp() returns NULL. 2) Assign fhandler_pty_slave for /dev/tty if CTTY is a pty in fh_alloc(). Fixes: 3721a756b0d8 ("Cygwin: console: Make the console accessible from other terminals."). Fixes: 23771fa1f7028 ("dtable.cc (fh_alloc): Make different decisions when generating fhandler for not-opened devices. Add kludge to deal with opening /dev/tty.") Reported-by: Bruce Jerrick <bmj001@gmail.com> Reviewed-by: Corinna Vinschen <corinna@vinschen.de> Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp> Diff: --- winsup/cygwin/dtable.cc | 8 +++++++- winsup/cygwin/fhandler/console.cc | 6 ++++++ 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/winsup/cygwin/dtable.cc b/winsup/cygwin/dtable.cc index 18e0f3097..2aae2fd65 100644 --- a/winsup/cygwin/dtable.cc +++ b/winsup/cygwin/dtable.cc @@ -600,7 +600,13 @@ fh_alloc (path_conv& pc) case FH_TTY: if (!pc.isopen ()) { - fhraw = cnew_no_ctor (fhandler_console, -1); + if (CTTY_IS_VALID (myself->ctty)) + { + if (iscons_dev (myself->ctty)) + fhraw = cnew_no_ctor (fhandler_console, -1); + else + fhraw = cnew_no_ctor (fhandler_pty_slave, -1); + } debug_printf ("not called from open for /dev/tty"); } else if (!CTTY_IS_VALID (myself->ctty) && last_tty_dev diff --git a/winsup/cygwin/fhandler/console.cc b/winsup/cygwin/fhandler/console.cc index 7768a9941..6aa3b50bf 100644 --- a/winsup/cygwin/fhandler/console.cc +++ b/winsup/cygwin/fhandler/console.cc @@ -4554,6 +4554,12 @@ fhandler_console::set_disable_master_thread (bool x, fhandler_console *cons) int fhandler_console::fstat (struct stat *st) { + /* When stat() is called, fh_alloc() in dtable.cc omits to initialize + the console instance. Due to this, get_ttyp() returns NULL here. + So, calling set_unit() is necessary to access getsid(). */ + if (!get_ttyp ()) + set_unit (); + fhandler_base::fstat (st); st->st_mode = S_IFCHR | S_IRUSR | S_IWUSR; pinfo p (get_ttyp ()->getsid ());
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