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: [<f811a089>] 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:[<f811a089>] 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] [<f806e68e>] ? serial_activate+0x2e/0x70 [usbserial]
[ 199.698511] [<f806e6ab>] serial_activate+0x4b/0x70 [usbserial]
[ 199.698521] [<c126380c>] tty_port_open+0x7c/0xd0
[ 199.698527] [<f806e660>] ? serial_set_termios+0xa0/0xa0 [usbserial]
[ 199.698534] [<f806e76f>] serial_open+0x2f/0x70 [usbserial]
[ 199.698540] [<c125d07c>] tty_open+0x20c/0x510
[ 199.698546] [<c10e9eb7>] chrdev_open+0xe7/0x230
[ 199.698553] [<c10e48f2>] __dentry_open+0x1f2/0x390
[ 199.698559] [<c144bfec>] ? _raw_spin_unlock+0x2c/0x50
[ 199.698565] [<c10e4b76>] nameidata_to_filp+0x66/0x80
[ 199.698570] [<c10e9dd0>] ? cdev_put+0x20/0x20
[ 199.698576] [<c10f3e08>] do_last+0x198/0x730
[ 199.698581] [<c10f4440>] path_openat+0xa0/0x350
[ 199.698587] [<c10f47d5>] do_filp_open+0x35/0x80
[ 199.698593] [<c144bfec>] ? _raw_spin_unlock+0x2c/0x50
[ 199.698599] [<c10ff110>] ? alloc_fd+0xc0/0x100
[ 199.698605] [<c10f0b72>] ? getname_flags+0x72/0x120
[ 199.698611] [<c10e4450>] do_sys_open+0xf0/0x1c0
[ 199.698617] [<c11fcc08>] ? trace_hardirqs_on_thunk+0xc/0x10
[ 199.698623] [<c10e458e>] sys_open+0x2e/0x40
[ 199.698628] [<c144c990>] 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: [<f811a089>] 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 <csuhgw@xxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
---
v2: clear disconnected flag before registering console
drivers/usb/serial/usb-serial.c | 8 ++++++++
1 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 63ba47d..4f3e52b 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -1063,6 +1063,12 @@ 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;
@@ -1087,6 +1093,8 @@ int usb_serial_probe(struct usb_interface *interface,
}
}
+ serial->disconnected = 0;
+
usb_serial_console_init(debug, minor);
exit:
--
1.7.8.4
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