Upstream fix that will be included in the another release of pcsclite.

From abe436e38aa58cb1140eff0d497ba721474c7703 Mon Sep 17 00:00:00 2001

From: Ludovic Rousseau <[email protected]>

Date: Sun, 24 Apr 2016 18:46:53 +0200

Subject: [PATCH] Fix signal handler by using only allowed functions

The signals are now treated in a special thread created just for that purpose.

Thanks to Andre Florath for the bug report

https://lists.alioth.debian.org/pipermail/pcsclite-muscle/Week-of-Mon-20160404/000561.html

[Pcsclite-muscle] pcscd jams when using '--auto-exit'

Andre Florath andre at florath.net

Sat Apr 9 06:06:44 UTC 2016

Hello!

Since some time I have problems with pcscd. I'm using pcscd in

conjunction with online banking and after a short period of working it

stops and jams the banking application.

A 'strace' to the pcscd showed that it is still running somewhere

deep in the USB stack.

The problem is, when manually running the the pcscd, there is no

problem at all - only when running from systemd.

Therefore I searched for the differences and found one: the

'--auto-exit'. Downloaded the source and had a closer look.

What I understand from the source code is, that when '--auto-exit' is

given, a SIGALRM is generated which (should) terminate the process.

I have noticed that the signal handler 'signal_trap()' uses some

function calls that are not allowed in signal handlers; like:

* syslog()

* gettimeofday()

* remove()

Using this creates undefined behavior.

(Please see 'man 7 signal' for a complete list of system calls that

are not allowed in signal handlers.)

I found a workaround for the issue.

Changed the service file to:

===

[Unit]

Description=PC/SC Smart Card Daemon

[Service]

ExecStart=/usr/sbin/pcscd --foreground --debug -a

ExecReload=/usr/sbin/pcscd --hotplug

[Install]

Also=pcscd.socket

===

and disabling the pcscd.socket gives me a stable system.

(Yes - pcscd is now started at boot time and runs the whole time

 - which is fine for me.)

If you need more information, please drop me a note.

Kind regards

Andre

---

 src/pcscdaemon.c | 170 ++++++++++++++++++++++++++++++++++++-------------------

 1 file changed, 111 insertions(+), 59 deletions(-)

diff --git a/src/pcscdaemon.c b/src/pcscdaemon.c

index 791f7f6..624e759 100644

--- a/src/pcscdaemon.c

+++ b/src/pcscdaemon.c

@@ -81,6 +81,7 @@ char SocketActivated = FALSE;

 static int ExitValue = EXIT_FAILURE;

 int HPForceReaderPolling = 0;

 static int pipefd[] = {-1, -1};

+static int signal_handler_fd[] = {-1, -1};

 char Add_Serial_In_Name = TRUE;

 char Add_Interface_In_Name = TRUE;

@@ -89,7 +90,6 @@ char Add_Interface_In_Name = TRUE;

  */

 static void at_exit(void);

 static void clean_temp_files(void);

-static void signal_reload(int sig);

 static void signal_trap(int);

 static void print_version (void);

 static void print_usage (char const * const);

@@ -152,6 +152,10 @@ static void SVCServiceRunLoop(void)

 			/* Nothing to do in case of a syscall interrupted

 			 * It happens when SIGUSR1 (reload) or SIGINT (Ctrl-C) is received

 			 * We just try again */

+

+			/* we wait a bit so that the signal handler thread can do

+			 * its job and set AraKiri if needed */

+			SYS_USleep(1000);

 			break;

 		default:

@@ -162,6 +166,93 @@ static void SVCServiceRunLoop(void)

 	}

 }

+/**

+ * thread dedicated to handle signals

+ *

+ * a signal handler can not call any function. See signal(7) for a list

+ * of function that are safe to call from a signal handler.

+ * The functions syslog(), gettimeofday() and remove() are NOT safe.

+ */

+static void *signal_thread(void *arg)

+{

+	(void)arg;

+

+	while (TRUE)

+	{

+		int r;

+		int sig;

+

+		r = read(signal_handler_fd[0], &sig, sizeof sig);

+		if (r < 0)

+		{

+			Log2(PCSC_LOG_ERROR, "read failed: %s", strerror(errno));

+			return NULL;

+		}

+

+		Log2(PCSC_LOG_INFO, "Received signal: %d", sig);

+

+		/* signal for hotplug */

+		if (SIGUSR1 == sig)

+		{

+#ifdef USE_USB

+			if (! AraKiri)

+				HPReCheckSerialReaders();

+#endif

+			/* Reenable the signal handler.

+			 * This is needed on Solaris and HPUX. */

+			(void)signal(SIGUSR1, signal_trap);

+

+			continue;

+		}

+

+		/* do not wait if asked to terminate

+		 * avoids waiting after the reader(s) in shutdown for example */

+		if (SIGTERM == sig)

+		{

+			Log1(PCSC_LOG_INFO, "Direct suicide");

+			at_exit();

+		}

+

+		if (SIGALRM == sig)

+		{

+			/* normal exit without error */

+			ExitValue = EXIT_SUCCESS;

+		}

+

+		/* the signal handler is called several times for the same Ctrl-C */

+		if (AraKiri == FALSE)

+		{

+			Log1(PCSC_LOG_INFO, "Preparing for suicide");

+			AraKiri = TRUE;

+

+			/* if still in the init/loading phase the AraKiri will not be

+			 * seen by the main event loop

+			 */

+			if (Init)

+			{

+				Log1(PCSC_LOG_INFO, "Suicide during init");

+				at_exit();

+			}

+		}

+		else

+		{

+			/* if pcscd do not want to die */

+			static int lives = 2;

+

+			lives--;

+			/* no live left. Something is blocking the normal death. */

+			if (0 == lives)

+			{

+				Log1(PCSC_LOG_INFO, "Forced suicide");

+				at_exit();

+			}

+		}

+	}

+

+	return NULL;

+}

+

+

 int main(int argc, char **argv)

 {

 	int rv;

@@ -515,6 +606,20 @@ int main(int argc, char **argv)

 	/* exits on SIGALARM to allow pcscd to suicide if not used */

 	(void)signal(SIGALRM, signal_trap);

+	if (pipe(signal_handler_fd) == -1)

+	{

+		Log2(PCSC_LOG_CRITICAL, "pipe() failed: %s", strerror(errno));

+		return EXIT_FAILURE;

+	}

+

+	pthread_t signal_handler_thread;

+	rv = pthread_create(&signal_handler_thread, NULL, signal_thread, NULL);

+	if (rv)

+	{

+		Log2(PCSC_LOG_CRITICAL, "pthread_create failed: %s", strerror(rv));

+		return EXIT_FAILURE;

+	}

+

 	/*

 	 * If PCSCLITE_IPC_DIR does not exist then create it

 	 */

@@ -610,7 +715,7 @@ int main(int argc, char **argv)

 	/*

 	 * Hotplug rescan

 	 */

-	(void)signal(SIGUSR1, signal_reload);

+	(void)signal(SIGUSR1, signal_trap);

 	/*

 	 * Initialize the comm structure

@@ -730,66 +835,13 @@ static void clean_temp_files(void)

 			strerror(errno));

 }

-static void signal_reload(/*@unused@*/ int sig)

-{

-	(void)signal(SIGUSR1, signal_reload);

-

-	(void)sig;

-

-	if (AraKiri)

-		return;

-

-#ifdef USE_USB

-	HPReCheckSerialReaders();

-#endif

-} /* signal_reload */

-

 static void signal_trap(int sig)

 {

-	Log2(PCSC_LOG_INFO, "Received signal: %d", sig);

-

-	/* do not wait if asked to terminate

-	 * avoids waiting after the reader(s) in shutdown for example */

-	if (SIGTERM == sig)

-	{

-		Log1(PCSC_LOG_INFO, "Direct suicide");

-		at_exit();

-	}

-

-	if (SIGALRM == sig)

-	{

-		/* normal exit without error */

-		ExitValue = EXIT_SUCCESS;

-	}

-

-	/* the signal handler is called several times for the same Ctrl-C */

-	if (AraKiri == FALSE)

-	{

-		Log1(PCSC_LOG_INFO, "Preparing for suicide");

-		AraKiri = TRUE;

-

-		/* if still in the init/loading phase the AraKiri will not be

-		 * seen by the main event loop

-		 */

-		if (Init)

-		{

-			Log1(PCSC_LOG_INFO, "Suicide during init");

-			at_exit();

-		}

-	}

-	else

-	{

-		/* if pcscd do not want to die */

-		static int lives = 2;

+	int r;

-		lives--;

-		/* no live left. Something is blocking the normal death. */

-		if (0 == lives)

-		{

-			Log1(PCSC_LOG_INFO, "Forced suicide");

-			at_exit();

-		}

-	}

+	r = write(signal_handler_fd[1], &sig, sizeof sig);

+	if (r < 0)

+		Log2(PCSC_LOG_ERROR, "write failed: %s", strerror(errno));

 }

 static void print_version (void)

-- 

1.9.1