2.6.0-test11 - fork, dup, dup2 oddities

2.6.0-test11 - fork, dup, dup2 oddities

[Lukas Hejtmanek]

Hello,

I have 2.6.0-test11 kernel. I try to run pppd with pppd call gprs. In gprs
I have device /dev/ttyUSB0. It fails. I've found that it happened ONLY if I use
detach option. 

I have tried /dev/ircomm0 as well with the same result. However with /dev/ttySL0
(that is symlink to pty created by modem driver) it works ok with or withoud
detach option.

I've tried to debug pppd and discovered failing code:

    /* make sure fds 0, 1, 2 are occupied */
    while ((fd = dup(in)) >= 0) {
        if (fd > 2) {
            close(fd);
            break;
        }
    }

    /* dup in and out to fds > 2 */
    {
        int fd1 = in, fd2 = out, fd3 = log_to_fd;

        in = dup(in);
        out = dup(out);
        if (log_to_fd >= 0) {
            errfd = dup(log_to_fd);
        } else {
            errfd = open(_PATH_CONNERRS, O_WRONLY | O_APPEND | O_CREAT, 0600);
        }
        close(fd1);
        close(fd2);
        close(fd3);
    }

    /* close fds 0 - 2 and any others we can think of */
    close(0);
    close(1);
    close(2);
    if (the_channel->close)
        (*the_channel->close)();
    closelog();
    close(fd_devnull);

    /* dup the in, out, err fds to 0, 1, 2 */
    dup2(in, 0);
    close(in);
    dup2(out, 1);
    close(out);
    if (errfd >= 0) {
        dup2(errfd, 2);
        close(errfd);
    }

    setuid(uid);
    if (getuid() != uid) {
        error("setuid failed");
        exit(1);
    }
    setgid(getgid());
    execl("/bin/sh", "sh", "-c", program, (char *)0);
    error("could not exec /bin/sh: %m");
    exit(99);

execl exit with code 02. 

program is equal to:
/usr/sbin/chat -V -s '' ATZ OK 'AT+CGDCONT=1,\"IP\",\"ointernet\"' OK 'ATD*99***1#' CONNECT

in=10, out=10 (it is opened /dev/ttyUSB0)

It works OK with 2.4.22 or if do not use previous fork.

-- 
Lukáš Hejtmánek

Re: 2.6.0-test11 - fork, dup, dup2 oddities

[Greg KH]

On Sun, Dec 07, 2003 at 10:03:05PM +0100, Lukas Hejtmanek wrote:
> Hello,
> 
> I have 2.6.0-test11 kernel. I try to run pppd with pppd call gprs. In gprs
> I have device /dev/ttyUSB0. It fails. I've found that it happened ONLY
> if I use detach option. 

The ttyUSB* nodes right now have a bug that prevents more than one
open() to work properly.  Well actually, the bug is on the close()
part...

Anyway, can you try the patch I posted here yesterday?  A copy of it is
below.  It should fix this bug.  Please let me know either way.

thanks,

greg k-h


diff -Nru a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
--- a/drivers/usb/serial/usb-serial.c	Fri Dec  5 17:37:16 2003
+++ b/drivers/usb/serial/usb-serial.c	Fri Dec  5 17:37:16 2003
@@ -493,12 +493,15 @@
 	return retval;
 }
 
-static void __serial_close(struct usb_serial_port *port, struct file *filp)
+static void serial_close(struct tty_struct *tty, struct file * filp)
 {
-	if (!port->open_count) {
-		dbg ("%s - port not opened", __FUNCTION__);
+	struct usb_serial_port *port = (struct usb_serial_port *) tty->driver_data;
+	struct usb_serial *serial = get_usb_serial (port, __FUNCTION__);
+
+	if (!serial)
 		return;
-	}
+
+	dbg("%s - port %d", __FUNCTION__, port->number);
 
 	--port->open_count;
 	if (port->open_count <= 0) {
@@ -506,30 +509,18 @@
 		 * port is being closed by the last owner */
 		port->serial->type->close(port, filp);
 		port->open_count = 0;
+
+		if (port->tty) {
+			if (port->tty->driver_data)
+				port->tty->driver_data = NULL;
+			port->tty = NULL;
+		}
 	}
 
 	module_put(port->serial->type->owner);
 	kobject_put(&port->serial->kobj);
 }
 
-static void serial_close(struct tty_struct *tty, struct file * filp)
-{
-	struct usb_serial_port *port = (struct usb_serial_port *) tty->driver_data;
-	struct usb_serial *serial = get_usb_serial (port, __FUNCTION__);
-
-	if (!serial)
-		return;
-
-	dbg("%s - port %d", __FUNCTION__, port->number);
-
-	/* if disconnect beat us to the punch here, there's nothing to do */
-	if (tty && tty->driver_data) {
-		__serial_close(port, filp);
-		tty->driver_data = NULL;
-	}
-	port->tty = NULL;
-}
-
 static int serial_write (struct tty_struct * tty, int from_user, const unsigned char *buf, int count)
 {
 	struct usb_serial_port *port = (struct usb_serial_port *) tty->driver_data;
@@ -848,19 +839,6 @@
 	dbg ("%s - %s", __FUNCTION__, kobj->name);
 
 	serial = to_usb_serial(kobj);
-
-	/* fail all future close/read/write/ioctl/etc calls */
-	for (i = 0; i < serial->num_ports; ++i) {
-		port = serial->port[i];
-		if (port->tty != NULL) {
-			port->tty->driver_data = NULL;
-			while (port->open_count > 0) {
-				__serial_close(port, NULL);
-			}
-			port->tty = NULL;
-		}
-	}
-
 	serial_shutdown (serial);
 
 	/* return the minor range that this device had */
@@ -1242,7 +1220,7 @@
 	/* register all of the individual ports with the driver core */
 	for (i = 0; i < num_ports; ++i) {
 		port = serial->port[i];
-		port->dev.parent = &serial->dev->dev;
+		port->dev.parent = &interface->dev;
 		port->dev.driver = NULL;
 		port->dev.bus = &usb_serial_bus_type;
 		port->dev.release = &port_release;

Re: 2.6.0-test11 - fork, dup, dup2 oddities

[Lukas Hejtmanek]

On Sun, Dec 07, 2003 at 04:46:55PM -0800, Greg KH wrote:
> The ttyUSB* nodes right now have a bug that prevents more than one
> open() to work properly.  Well actually, the bug is on the close()
> part...
> 
> Anyway, can you try the patch I posted here yesterday?  A copy of it is
> below.  It should fix this bug.  Please let me know either way.

Thanks, this patch works for me. pppd now correctly connect via ttyUSB. 

However similar patch will be need for ircomm-tty. That is not functional as
well.

-- 
Lukáš Hejtmánek