From: Johan Hovold Date: Tue, 20 Mar 2012 15:59:33 +0000 (+0100) Subject: USB: serial: fix race between probe and open X-Git-Url: http://git.alex.org.uk USB: serial: fix race between probe and open BugLink: http://bugs.launchpad.net/bugs/987337 commit a65a6f14dc24a90bde3f5d0073ba2364476200bf upstream. Fix race between probe and open by making sure that the disconnected flag is not cleared until all ports have been registered. A call to tty_open while probe is running may get a reference to the serial structure in serial_install before its ports have been registered. This may lead to usb_serial_core calling driver open before port is fully initialised. With ftdi_sio this result in the following NULL-pointer dereference as the private data has not been initialised at open: [ 199.698286] IP: [] ftdi_open+0x59/0xe0 [ftdi_sio] [ 199.698297] *pde = 00000000 [ 199.698303] Oops: 0000 [#1] PREEMPT SMP [ 199.698313] Modules linked in: ftdi_sio usbserial [ 199.698323] [ 199.698327] Pid: 1146, comm: ftdi_open Not tainted 3.2.11 #70 Dell Inc. Vostro 1520/0T816J [ 199.698339] EIP: 0060:[] EFLAGS: 00010286 CPU: 0 [ 199.698344] EIP is at ftdi_open+0x59/0xe0 [ftdi_sio] [ 199.698348] EAX: 0000003e EBX: f5067000 ECX: 00000000 EDX: 80000600 [ 199.698352] ESI: f48d8800 EDI: 00000001 EBP: f515dd54 ESP: f515dcfc [ 199.698356] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 [ 199.698361] Process ftdi_open (pid: 1146, ti=f515c000 task=f481e040 task.ti=f515c000) [ 199.698364] Stack: [ 199.698368] f811a9fe f811a9e0 f811b3ef 00000000 00000000 00001388 00000000 f4a86800 [ 199.698387] 00000002 00000000 f806e68e 00000000 f532765c f481e040 00000246 22222222 [ 199.698479] 22222222 22222222 22222222 f5067004 f5327600 f5327638 f515dd74 f806e6ab [ 199.698496] Call Trace: [ 199.698504] [] ? serial_activate+0x2e/0x70 [usbserial] [ 199.698511] [] serial_activate+0x4b/0x70 [usbserial] [ 199.698521] [] tty_port_open+0x7c/0xd0 [ 199.698527] [] ? serial_set_termios+0xa0/0xa0 [usbserial] [ 199.698534] [] serial_open+0x2f/0x70 [usbserial] [ 199.698540] [] tty_open+0x20c/0x510 [ 199.698546] [] chrdev_open+0xe7/0x230 [ 199.698553] [] __dentry_open+0x1f2/0x390 [ 199.698559] [] ? _raw_spin_unlock+0x2c/0x50 [ 199.698565] [] nameidata_to_filp+0x66/0x80 [ 199.698570] [] ? cdev_put+0x20/0x20 [ 199.698576] [] do_last+0x198/0x730 [ 199.698581] [] path_openat+0xa0/0x350 [ 199.698587] [] do_filp_open+0x35/0x80 [ 199.698593] [] ? _raw_spin_unlock+0x2c/0x50 [ 199.698599] [] ? alloc_fd+0xc0/0x100 [ 199.698605] [] ? getname_flags+0x72/0x120 [ 199.698611] [] do_sys_open+0xf0/0x1c0 [ 199.698617] [] ? trace_hardirqs_on_thunk+0xc/0x10 [ 199.698623] [] sys_open+0x2e/0x40 [ 199.698628] [] sysenter_do_call+0x12/0x36 [ 199.698632] Code: 85 89 00 00 00 8b 16 8b 4d c0 c1 e2 08 c7 44 24 14 88 13 00 00 81 ca 00 00 00 80 c7 44 24 10 00 00 00 00 c7 44 24 0c 00 00 00 00 <0f> b7 41 78 31 c9 89 44 24 08 c7 44 24 04 00 00 00 00 c7 04 24 [ 199.698884] EIP: [] ftdi_open+0x59/0xe0 [ftdi_sio] SS:ESP 0068:f515dcfc [ 199.698893] CR2: 0000000000000078 [ 199.698925] ---[ end trace 77c43ec023940cff ]--- Reported-and-tested-by: Ken Huang Signed-off-by: Johan Hovold Signed-off-by: Greg Kroah-Hartman Signed-off-by: Tim Gardner --- diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c index cc274fd..38d7ebd 100644 --- a/drivers/usb/serial/usb-serial.c +++ b/drivers/usb/serial/usb-serial.c @@ -1059,6 +1059,12 @@ int usb_serial_probe(struct usb_interface *interface, serial->attached = 1; } + /* Avoid race with tty_open and serial_install by setting the + * disconnected flag and not clearing it until all ports have been + * registered. + */ + serial->disconnected = 1; + if (get_free_serial(serial, num_ports, &minor) == NULL) { dev_err(&interface->dev, "No more free serial devices\n"); goto probe_error; @@ -1083,6 +1089,8 @@ int usb_serial_probe(struct usb_interface *interface, } } + serial->disconnected = 0; + usb_serial_console_init(debug, minor); exit: