From: Takashi Yano <takashi.yano@nifty.ne.jp>
To: cygwin-patches@cygwin.com
Subject: [PATCH 4/4] Cygwin: console: Fix potential deadlock regarding acuqiring mutex.
Date: Thu, 13 Jan 2022 21:28:11 +0900 [thread overview]
Message-ID: <20220113122811.241-5-takashi.yano@nifty.ne.jp> (raw)
In-Reply-To: <20220113122811.241-1-takashi.yano@nifty.ne.jp>
- Acquiring input_mutex and attach_mutex in console code has potential
risk of deadlock. This patch fixes the issue.
---
winsup/cygwin/fhandler.h | 2 ++
winsup/cygwin/select.cc | 7 ++++---
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index 0cea1b7f3..fb4747608 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -2208,9 +2208,11 @@ private:
void acquire_input_mutex_if_necessary (DWORD ms)
{
acquire_input_mutex (ms);
+ acquire_attach_mutex (ms);
}
void release_input_mutex_if_necessary (void)
{
+ release_attach_mutex ();
release_input_mutex ();
}
diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
index 5b8fc0f81..d01a319ef 100644
--- a/winsup/cygwin/select.cc
+++ b/winsup/cygwin/select.cc
@@ -1122,29 +1122,30 @@ peek_console (select_record *me, bool)
HANDLE h;
set_handle_or_return_if_not_open (h, me);
+ fh->acquire_input_mutex (mutex_timeout);
acquire_attach_mutex (mutex_timeout);
while (!fh->input_ready && !fh->get_cons_readahead_valid ())
{
if (fh->bg_check (SIGTTIN, true) <= bg_eof)
{
release_attach_mutex ();
+ fh->release_input_mutex ();
return me->read_ready = true;
}
else if (!PeekConsoleInputW (h, &irec, 1, &events_read) || !events_read)
break;
- fh->acquire_input_mutex (mutex_timeout);
if (fhandler_console::input_winch == fh->process_input_message ()
&& global_sigs[SIGWINCH].sa_handler != SIG_IGN
&& global_sigs[SIGWINCH].sa_handler != SIG_DFL)
{
set_sig_errno (EINTR);
- fh->release_input_mutex ();
release_attach_mutex ();
+ fh->release_input_mutex ();
return -1;
}
- fh->release_input_mutex ();
}
release_attach_mutex ();
+ fh->release_input_mutex ();
if (fh->input_ready || fh->get_cons_readahead_valid ())
return me->read_ready = true;
--
2.34.1
next prev parent reply other threads:[~2022-01-13 12:29 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-13 12:28 [PATCH 0/4] Some fixes for console and pty Takashi Yano
2022-01-13 12:28 ` [PATCH 1/4] Cygwin: pty, console: Fix deadlock in GDB regarding mutex Takashi Yano
2022-01-13 12:28 ` [PATCH 2/4] Cygwin: pty: Fix memory leak in master_fwd_thread Takashi Yano
2022-01-13 12:28 ` [PATCH 3/4] Cygwin: pty: Stop closing and recreating attach_mutex Takashi Yano
2022-01-13 12:28 ` Takashi Yano [this message]
2022-01-14 9:15 ` [PATCH 0/4] Some fixes for console and pty Corinna Vinschen
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