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tty: Fix a USB serial crash/scribble 

The port lock is used to protect the port state. However the port structure
is freed on a hangup, then the lock taken on a close. The right fix is to
drop the port on tty->shutdown() but we can't yet do that due to sleep v
non-sleeping rules. Instead do the next best thing and fix it up when we are
not in -rc season.

Reported-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Tested-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alan Cox 2009-07-27 10:58:08 +01:00 committed by Linus Torvalds
parent 6a31d4aeab
commit b68f2fb9e7
1 changed files with 18 additions and 1 deletions
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19
drivers/usb/serial/usb-serial.c
View File

@ -340,6 +340,22 @@ static void serial_close(struct tty_struct *tty, struct file *filp)
dbg("%s - port %d", __func__, port->number);
/* FIXME:
This leaves a very narrow race. Really we should do the
serial_do_free() on tty->shutdown(), but tty->shutdown can
be called from IRQ context and serial_do_free can sleep.
The right fix is probably to make the tty free (which is rare)
and thus tty->shutdown() occur via a work queue and simplify all
the drivers that use it.
*/
if (tty_hung_up_p(filp)) {
/* serial_hangup already called serial_down at this point.
Another user may have already reopened the port but
serial_do_free is refcounted */
serial_do_free(port);
return;
}
if (tty_port_close_start(&port->port, tty, filp) == 0)
return;
@ -355,7 +371,8 @@ static void serial_hangup(struct tty_struct *tty)
struct usb_serial_port *port = tty->driver_data;
serial_do_down(port);
tty_port_hangup(&port->port);
serial_do_free(port);
/* We must not free port yet - the USB serial layer depends on it's
continued existence */
}
static int serial_write(struct tty_struct *tty, const unsigned char *buf,