From 441ca95fef3516d70b2a8339f72b645e76683174 Mon Sep 17 00:00:00 2001 From: Takashi Yano Date: Thu, 13 Jan 2022 20:57:15 +0900 Subject: [PATCH] Cygwin: console: Fix potential deadlock regarding acuqiring mutex. - 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 630293ff8..4226bfd69 100644 --- a/winsup/cygwin/fhandler.h +++ b/winsup/cygwin/fhandler.h @@ -2209,9 +2209,11 @@ 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;